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Salinity selection and preference of the grey snapper Lutjanus griseus: Field and laboratory observations
Abstract
Field observations were supplemented with laboratory experiments to reveal patterns of salinity selection and preference for grey snapper Lutjanus griseus (c. 21 cm total length, L(T)), an ecologically and economically important species in the south-eastern U.S.A. Fish abundance data were examined from a long-term field survey conducted in the mangrove habitats of Biscayne Bay, Florida, where salinities ranged from <1 to 40. First, regression analyses indicated significant, positive linear relationships with salinity for both L. griseus frequency of occurrence and concentration (density when present). These patterns are inconsistent with physiological expectations of minimizing energetic osmoregulatory costs. Next, the salinity preference and swimming activity of 11 L. griseus (ranging from 18 to 23 cm L(T)) were investigated using a newly developed electronic shuttlebox system. In the laboratory, fish preferred intermediate salinities in the range of 9-23. Swimming activity (measured in terms of spontaneous swimming speed) followed a parabolic relationship with salinity, with reduced activity at salinity extremes perhaps reflecting compensation for higher osmoregulatory costs. It is suspected that the basis of the discrepancy between laboratory and field observations for size classes at or near maturity ultimately relates to the reproductive imperative to move towards offshore (high-salinity) coral-reef habitats, a necessity that probably overrides the strategy of minimizing osmoregulatory energetic costs.
... Furthermore, the water may be mixed horizontally by animal movement, which may render subsequent occurrence analyses imprecise. Issues with unwanted water mixing and stratification can be reduced significantly by having physically separated choice chambers that are interconnected by narrow passages for the animal, such as so-called shuttle-boxes, which provides stable water separation for a variety of environmental variables (Schurmann et al., 1991;Serrano et al., 2010;Kates et al., 2012;Borowiec et al., 2018). ...
... Over time, the shuttle-box has been redeveloped significantly both with respect to basic set up and experimental application (e.g. Reynolds, 1977;Schurmann and Christiansen, 1994;Serrano et al., 2010;Herbert et al., 2012;Kates et al., 2012;Cooper et al., 2018). The many different directions of use of the system may affect repeatability and comparability of studies, and we have therefore systematically reviewed the use of shuttle-boxes for determining environmental preference and avoidance by aquatic animals. ...
... changes between nighttime and daytime environmental preference (e.g. Serrano et al., 2010) or feeding (Reynolds and Casterlin 1979a). However, the 'unusual' events may also be caused by random effects, e.g. ...
Animals' selection of environments within a preferred range is key to understanding their habitat selection, tolerance to stressors and responses to environmental change. For aquatic animals, preferred environmental ranges can be studied in so-called shuttle-boxes, where an animal can choose its ambient environment by shuttling between separate choice chambers with differences in an environmental variable. Over time, researchers have refined the shuttle-box technology and applied them in many different research contexts, and we here review the use of shuttle-boxes as a research tool with aquatic animals over the past 50 years. Most studies on the methodology have been published in the latest decade, probably due to an increasing research interest in the effects of environmental change, which underlines the current popularity of the system. The shuttle-box has been applied to a wide range of research topics with regards to preferred ranges of temperature, CO
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, salinity and O
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in a vast diversity of species, showing broad applicability for the system. We have synthesized the current state-of-the-art of the methodology and provided best practice guidelines with regards to setup, data analyses, experimental design and study reporting. We have also identified a series of knowledge gaps, which can and should be addressed in future studies. We conclude with highlighting directions for research using shuttle-boxes within evolutionary biology and behavioural and physiological ecology.
... Because tropical marine fishes may incorporate metabolic carbon to the otolith, an adjustment was also investigated to account for trophic level depletion (typically from approximately -3‰ to -5‰ for tropical marine fishes; e.g., Andrews et al. 2013a;Barnett et al. 2018). These salinity estimates were compared with empirical evidence from the settlement habitat of juvenile gray snapper (Starck and Schroeder 1971;Wuenschel et al. 2004;Serrano et al. 2010) to verify the applicability of the freshwater 14 C dilution concept. ...
... Freshwater DIC is 13 C-depleted relative to marine DIC and follows a linear trend with salinity during mixing in an estuary (Chanton and Lewis 1999). Hence, the lowest δ 13 C values of -9.0‰ to -9.9‰ for GS-09 were adjusted by 3.4‰ to -5.6 to -6.5‰ with a corresponding environmental salinity estimate of 10-12, versus~1-3 without an adjustment-the latter values are lower than the salinity preferred by juvenile gray snapper (~9-23, Serrano et al. 2010; Figure 4). were depleted and cover nearly the full southwestern edge of the aquifer. ...
... This estimate is consistent with observations of environmental salinity for juvenile gray snapper (Starck and Schroeder 1971), as well as the early life history settlement habitat that is typically associated with estuarine waters (Chester and Thayer 1990;Allman and Grimes 2002). Gray snapper is well-adapted to low salinity in their early life history (Wuenschel et al. 2004) with an affinity for salinity near 9-23 for juvenile fish (Serrano et al. 2010). Hence, it is important to consider the life history and regional hydrogeology for otoliths of fishes for not only bomb 14 C age validation studies, but for archaeological work on midden otoliths when determining true radiocarbon age and potential dates of site occupation (e.g., Disspain et al. 2017). ...
The otoliths (ear stones) of fishes are commonly used to describe the age and growth of marine and freshwater fishes. These non-skeletal structures are fortuitous in their utility by being composed of mostly inorganic carbonate that is inert through the life of the fish. This conserved record functions like an environmental chronometer and bomb-produced radiocarbon — a 14C signal created by atmospheric testing of thermonuclear devices — can be used as a time-specific marker in validating fish age. However, complications from the hydrogeology of nearshore marine environments can complicate 14C levels, as was the case with gray snapper (Lutjanus griseus) along the Gulf of Mexico coast of Florida. Radiocarbon of these nearshore waters is influenced by freshwater input from the karst topography of the Upper Floridan Aquifer-estuarine waters that are 14C-depleted from surface and groundwater inputs. Some gray snapper likely recruited to this kind of environment where 14C levels were depleted in the earliest otolith growth, although age was validated for individuals that were not exposed to 14C-depleted waters to an age of at least 25 years with support for a 30-year lifespan.
... We observed that the seascape patterns significantly interacted with the salinity zones to modulate differences in faunal assemblage composition and diversity, highlighting the complexity and challenges faced when trying to understand the response of faunal assemblages to changes in their natural habitat. Our study included salinity regimes as an explanatory factor because salinity can influence both spatial attributes of SAV habitats (Santos et al. 2011) and faunal responses in Biscayne Bay (Serafy et al. 2003, Serrano et al. 2010, Browder et al. 2012. Salinity preferences and osmoregulation requirements can spatially limit animals to remain within specific salinity ranges and influence energy allocation (i.e. ...
... Salinity preferences and osmoregulation requirements can spatially limit animals to remain within specific salinity ranges and influence energy allocation (i.e. tradeoffs between growth, reproduction, motility, and habitat use; Hurst & Conover 2002, Serrano et al. 2010, McManus et al. 2014. Results from a salinity laboratory experiment using the most abundant nearshore fish species in Biscayne Bay suggested that the dif-ferential osmoregulatory abilities explain some, but not all, of the differences in distribution and abundance of fish assemblages in different salinity environments (Serafy et al. 1997). ...
... However, when salinity conditions are favorable, biotic interactions and demographic processes operating at the scale of the seascape may influence structure, diversity, and distribution patterns. This hierarchy of drivers was evidenced in our study for species such as F. duorarum, L. griseus, and L. rhomboides that have a wide salinity tolerance and were ubiquitous across our study area (Serafy et al. 1997, Santos 2010, Serrano et al. 2010. For these species, the highest contrast in abundance and biomass was observed between the seascape types (and not between salinity zones), especially within their optimal salinity regimes. ...
Anthropogenic disturbances in coastal and marine environments have resulted in the transformation of vegetated benthic habitat spatial patterns, which is thought to influence the distribution, community composition, and behavior of marine fauna. In Biscayne Bay, Florida, USA, freshwater discharges into nearshore areas have resulted in the fragmentation of the spatial patterning of submerged aquatic vegetation (SAV). To understand the ecological consequences of the freshwater-induced SAV seascape fragmentation, fish and crustaceans were sampled using seine nets across seascapes with continuous and highly fragmented SAV spatial configurations and across salinity regimes. Fragmented SAV seascapes supported significantly higher species diversity of fish and crustaceans, especially in areas influenced by freshwater discharges. Also, fragmented seascapes supported a higher abundance of the pink shrimp Farfantepenaeus duorarum and the goby Gobiosoma robustum, and higher biomass of generalist predatory fishes than seascapes with continuous SAV. In contrast, pinfish Lagodon rhomboides was more abundant in seascapes with continuous SAV. Faunal assemblage composition differed between zones of contrasting salinity regimes, and the contribution of species occurrence and abundance to the differentiation of assemblage composition between seascape types was associated with the salinity regimes of the seascapes. Thus, water salinity and spatial properties of SAV seascapes are factors that interact to influence faunal community structure in Biscayne Bay. These findings highlight the importance of understanding how environmental context (e.g. salinity regimes) can modulate the influence of benthic spatial patterning on the abundance and biodiversity of nekton communities.
... During the 1980s, a two-current choice flume system with video monitoring was developed and used to assess avoidance behaviour of fishes and invertebrates when exposed to waste water from a chemical plant (Randelov, Poulsen & Pedersen 1986). Other methods for presenting chemical cues include shuttle box systems ( Fig. 1c) with two connected circular arenas (Serrano, Grosell & Serafy 2010), two-choice plume flumes (Fig. 1d), where cues are released as plumes (Gardiner & Atema 2007), and regular aquaria with cues released at point sources (Caprio et al. 2014). These methods each have their advantages (e.g. ...
... Straight Y-mazes are generally small. The shuttle box system (d) consists of two circular tanks joined by a channel (Serrano et al. 2010). Slow circular currents keep the waters from mixing. ...
... For example, the density variation caused by a salinity difference of 6 PSU made laminar flow impossible in a flume with a 10 9 10 cm choice arena, regardless of water speed (Fig. 4). For choice experiments requiring differences in water density, shuttle box systems (Fig. 1) may provide more stable water separation (Serrano, Grosell & Serafy 2010). ...
Aquatic chemical ecology is an important and growing field of research that involves understanding how organisms perceive and respond to chemical cues in their environment. Research assessing the preference or avoidance of a water source containing specific chemical cues has increased in popularity in recent years, and a variety of methods have been described in the scientific literature. Two‐current choice flumes have seen the greatest increase in popularity, perhaps because of their potential to address the broadest range of research questions.
Here, we review the literature on two‐current choice flumes and show that there is a clear absence of standardized methodologies that make comparisons across studies difficult. Some of the main issues include turbulent flows that cause mixing of cues, inappropriate size of choice arenas for the animals, short experiments with stressed animals, failure to report how experiment and researcher biases were eliminated, general underreporting of methodological details, underutilization of collected data and inappropriate data analyses.
In this review, we present best practice guidelines on how to build, test and use two‐current choice flumes to measure the behavioural responses of aquatic animals to chemical cues, and provide blueprints for flume construction. The guidelines include steps that can be taken to avoid problems commonly encountered when using two‐current choice flumes and analysing the resulting data.
This review provides a set of standards that should be followed to ensure data quality, transparency and replicability in future studies in this field.
... Another variable that might explain the lack of predator avoidance behaviour in favour of osmoregulation could be the influence of salinity on swimming performance. Several studies have found decreases in activity levels and performance at salinities at the high end of the salinity tolerance range in various euryhaline species (Swanson, 1998;Edeline et al., 2005;Serrano et al., 2010). Changes in performance capabilities caused by abiotic factors (such as temperature) have been shown to change the behavioural strategies used during encounters with predators (Hertz et al., 1982;Gerald, 2008). ...
... 1766) would alter their salinity preference to enhance digestion to maintain calcium homeostasis. Also, Serrano et al. (2010) found inconsistencies between salinity preferences measured in the field and in the laboratory. They suggested that the need to use higher salinities for reproductive purposes outweighed the osmoregulatory costs (Serrano et al., 2010). ...
... Also, Serrano et al. (2010) found inconsistencies between salinity preferences measured in the field and in the laboratory. They suggested that the need to use higher salinities for reproductive purposes outweighed the osmoregulatory costs (Serrano et al., 2010). These studies, along with the present study, highlight the need to consider both ecological needs and osmoregulatory costs when attempting to explain how euryhalinity and stenohalinity evolved and are maintained in the various lineages of fishes. ...
Salinity preference and responses to predatory chemical cues were examined both separately and simultaneously in freshwater (FW) and saltwater (SW)-acclimated sailfin mollies Poecilia latipinna, a euryhaline species. It was hypothesized that P. latipinna would prefer FW over SW, move away from chemical cues from a crayfish predator, and favour predator avoidance over osmoregulation when presented with both demands. Both FW and SW-acclimated P. latipinna preferred FW and actively avoided predator cues. When presented with FW plus predator cues v. SW with no cues, P. latipinna were more often found in FW plus predator cues. These results raise questions pertaining to the potential osmoregulatory stress of salinity transitions in euryhaline fishes relative to the potential fitness benefits and whether euryhalinity is utilized for predator avoidance. This study sheds light on the potential benefits and consequences of being salt tolerant or intolerant and complicates the understanding of the selection pressures that have favoured the different osmoregulatory mechanisms among fishes.
... In compliance with the National Environmental Policy Act of 1969, the Nuclear Regulatory Commission (NRC) requires environmental impact assessments for the licensing of new and expanded nuclear power projects (NRC 10 CFR Part 51). Few studies consider potential impacts to the surrounding environment resulting from operation of recirculating cooling systems, such as those planned for the site discussed in this paper (e.g., Miner and Warrick 1974;Shrecker et al. 1975;Talbot 1979;Lin et al. 1994;Brujis and Jenner 2012). It has been suggested that the greatest risk to aquatic and estuarine ecosystems posed by cooling systems of thermoelectric power plants is caused by continuous exposure to sub-lethal stressors, such as changes in water quality, rather than the abrupt mortality of large numbers of organisms (Clark and Brownell 1973;Laws 2000;Kulkarni et al. 2011). ...
... The location of TPNGS, on Biscayne Bay, is of importance because Biscayne Bay's mangrove shoreline habitat is slated for restoration as part of the Biscayne Bay Coastal Wetlands project, a component of the Comprehensive Everglades Restoration Plan (CERP 2005(CERP , 2010 (i.e., McCaughran 1977;Smith et al. 1993;Chen et al. 2010), including several studies conducted over 40 years ago at TPNGS (Nugent 1970;Bader and Roessler 1971;Thorhaug and Roessler 1977;Thorhaug et al. 1979), the location of the present study. Water quality (inclusive of temperature and salinity) is known to be a driver of fine-scale spatial variation in nearshore fish communities of Biscayne Bay (Serafy et al. 1997(Serafy et al. , 2003(Serafy et al. , 2005Green et al. 2006;Faunce and Serafy 2007). ...
... Gray snapper is a commercially and recreationally important predator species in nearshore south Florida waters (SAFMC 2009). The ecological rationale of examining these two species is detailed in Serrano et al. 2010;McManus et al. 2014). However, the exercise of examining the capacity of the survey to detect change at the species-specific level was conducted to demonstrate the general capability of the survey at this level of resolution. ...
An expansion is underway of a nuclear power plant on the shoreline of Biscayne Bay, Florida, USA. While the precise effects of its construction and operation are unknown, impacts on surrounding marine habitats and biota are considered by experts to be likely. The objective of the present study was to determine the adequacy of an ongoing monitoring survey of fish communities associated with mangrove habitats directly adjacent to the power plant to detect fish community changes, should they occur, at three spatial scales. Using seasonally resolved data recorded during 532 fish surveys over an 8-year period, power analyses were performed for four mangrove fish metrics (fish diversity, fish density, and the occurrence of two ecologically important fish species: gray snapper (Lutjanus griseus) and goldspotted killifish (Floridichthys carpio). Results indicated that the monitoring program at current sampling intensity allows for detection of <33 % changes in fish density and diversity metrics in both the wet and the dry season in the two larger study areas. Sampling effort was found to be insufficient in either season to detect changes at this level (<33 %) in species-specific occurrence metrics for the two fish species examined. The option of supplementing ongoing, biological monitoring programs for improved, focused change detection deserves consideration from both ecological and cost-benefit perspectives.
... Part of the challenge is that pre-canal-system biological data are almost entirely lacking and, because organisms inhabiting coastal shoreline habitats typically must cope with large fluctuations in salinity, many possess remarkable tolerance of osmotic stress. However, high tolerance, conferred by physiological robustness does not necessarily equate to lack of affinity for a narrower range of environmental conditions than tolerance studies alone might suggest (Serrano et al., 2010). For fishes, one approach to revealing these affinities, if they exist, is to couple detailed analyses of field distribution and abundance data with laboratory-based behavioral studies, whereby fish are allowed to distribute themselves along a salinity gradient (Serrano et al., 2010;Bucking et al., 2012). ...
... However, high tolerance, conferred by physiological robustness does not necessarily equate to lack of affinity for a narrower range of environmental conditions than tolerance studies alone might suggest (Serrano et al., 2010). For fishes, one approach to revealing these affinities, if they exist, is to couple detailed analyses of field distribution and abundance data with laboratory-based behavioral studies, whereby fish are allowed to distribute themselves along a salinity gradient (Serrano et al., 2010;Bucking et al., 2012). ...
... Following Serafy et al. (2007) and Serrano et al. (2010), we applied the delta approach (appropriate when counts are dominated by zero values) to reveal goldspotted killifish abundance relationships with water temperature, salinity and depth. Two abundance metrics were analyzed: "occurrence" (the likelihood of encountering one or more F. carpio per 60 m 2 transect) and "concentration" (number of individuals per transect when F. carpio was present). ...
... Every fish species or fish variable considered in this study was related to one or more aspects of salinity although the timescale, strength, and direction of this association varied widely. Although many estuarine fishes are adapted to tolerate a euryhaline environment, they often seek to optimize their position in the estuary to maximize fitness directly by seeking physiologically suitable salinity (Sheaves 1996;Serafy et al. 1997;Serrano et al. 2010;Rubec et al. 2021), or through indirect processes such as use of energy sources that are affected by salinity (Montague and Ley 1993;Palmer et al. 2011Palmer et al. , 2015Vinagre et al. 2011;Lorenz 2014;Loh et al. 2017), avoidance of predators or pathogens, or migratory imperatives such as seeking spawning or recruitment habitat (Grange et al. 2000;Kanajembo et al. 2001;Jenkins et al. 2010;Serrano et al. 2010). In this study, aspects of salinity measured over longer time intervals of weeks to months best related to fish abundance. ...
... Every fish species or fish variable considered in this study was related to one or more aspects of salinity although the timescale, strength, and direction of this association varied widely. Although many estuarine fishes are adapted to tolerate a euryhaline environment, they often seek to optimize their position in the estuary to maximize fitness directly by seeking physiologically suitable salinity (Sheaves 1996;Serafy et al. 1997;Serrano et al. 2010;Rubec et al. 2021), or through indirect processes such as use of energy sources that are affected by salinity (Montague and Ley 1993;Palmer et al. 2011Palmer et al. , 2015Vinagre et al. 2011;Lorenz 2014;Loh et al. 2017), avoidance of predators or pathogens, or migratory imperatives such as seeking spawning or recruitment habitat (Grange et al. 2000;Kanajembo et al. 2001;Jenkins et al. 2010;Serrano et al. 2010). In this study, aspects of salinity measured over longer time intervals of weeks to months best related to fish abundance. ...
Changes in freshwater flow to estuaries can cause a suite of ecosystem impacts including eutrophication and alterations to plant communities, zooplankton populations, and other biota. In southwest Florida, historical manipulation of freshwater flow due to development, canals, and drainage ditches is pervasive. Because there are estuaries with reduced, increased, and relatively natural freshwater flow, this region presents an ideal system to study how these changes relate to downstream fish abundances. We used a 20-year trawl dataset focused on juvenile and small-bodied fish from three mangrove-lined sub-estuaries with contrasting flow conditions in southwest Florida’s Ten Thousand Islands to identify important environmental and temporal variables influencing fish populations. We used generalized additive models to investigate total fish abundance, species richness, diversity, and the abundances of 23 ecologically, recreationally, or commercially important species and describe their relationships with important environmental and temporal variables. While salinity and temperature had species-specific relationships with fish abundances, seasonality, interannual variability, and sub-estuary were more closely related to fish than salinity and temperature in most cases. Only 8 of 23 species responded most strongly to temperature, and only 1 species responded most strongly to salinity. This suggests that for most species in our study, temporal factors such as timing of spawning and recruitment variability had stronger relationships with the structure of fish populations than changes in freshwater flow. This work quantified how changes in freshwater flow, using salinity as a proxy, may relate to downstream fish abundances and therefore the potential implications of planned watershed restoration that is part of the Comprehensive Everglades Restoration Plan.
... Many other salinity preference studies infer behavioral salinity preference by analyzing geographic distribution of organisms relative to salinity (Scott 1982 with Scotian Shelf fish, Roberts et al 1997 with mosquito larvae, and Calliari 2007 with mysids). However, separating salinity effects from other biological, physical, and chemical factors is not possible in such studies (Serrano 2010). Here we consider salinity preference as a behavior, which must be determined experimentally by testing an organism's response to salinity. ...
... Factors affecting salinity preference in different fish species have been discovered experimentally, such as age, temperature, acclimation salinity (Fritz 1974, Baggerman 1957, reproductive status (Baggerman 1957), hormonal status (Audet 1985, Baggerman 1957, parasitic infection (Webster 2007), and dark/light ratio (Spieler 1976). Most of these studies examine salinity preference to better understand either species distributions (Buck 2011, Serrano 2010, Parkyn 2002, Moser 1989, Fritz 1974 or ontogenetic shifts in salinity preference in diadromous fish such as eels, galaxiids, salmon, and sticklebacks (Cook 2010, Edeline 2006, Crean 2005, McInerney 1963, Baggerman 1957. In this study we examine salinity preference between different populations acclimated to different salinities to test for population and acclimation effects. ...
Glacial retreat during the Pleistocene caused landlocking of anadromous Alaskan threespine stickleback, Gasterosteus aculeatus, furnishing a natural ‘experiment’ in osmoregulatory divergence. The objective of this study was to assess the effects of individual acclimation and population divergence on salinity preference. Full-sibling families of marine, anadromous, and freshwater-landlocked populations of stickleback were reared in common environments until 3 weeks post-hatch, then were split and acclimated to low or high salinity. At 6 to 8 weeks of age the six experimental groups were tested for salinity preference in a tank that offers fish a choice of compartments with different salinities arranged in a gradient from fresh to sea water. We observed significant population and acclimation effects. Anadromous fish preferred sea water and avoided fresh water, whether acclimated to low or high salinity. Landlocked fish showed a strong acclimation effect, avoiding salt water when acclimated to fresh and avoiding freshwater when acclimated to salt, while showing no preference for their acclimation salinity. Fish from the marine population showed little preference for fresh or sea water regardless of acclimation salinity. After restriction to fresh water for more than five thousand generations, landlocked fish have evolved weaker preferences in response to a salinity gradient compared to their anadromous ancestors.
... Schmidt et al. (1999) reported a significant positive relationship between catch rate of Gray Snapper and mean annual salinities in northern Florida Bay, suggesting that periods of higher salinities may lead to increased abundance of this species in ENP. Serrano et al. (2010) examined fish from 18 to 23 cm TL from near-shore marine (salinities of 30-34 PSU) habitats within Biscayne Bay and Florida Bay for salinity preferences and swimming speed in the lab. Individual fish revealed great variability in salinity preference, although intermediate salinities from 9-23 PSU were selected by all fish as their final preference. ...
... In testing for swimming speed efficiency at different salinities, Serrano et al. (2010) reported that swimming activity followed a parabolic relationship with salinity, with reduced activity at salinity extremes. They suggested that the relationship may have reflected compensation for higher osmoregulatory costs, in that fish should minimize overall energy consumption at extreme salinities to favor energetic costs needed for osmoregulation. ...
To supplement information needed to support Essential Fish Habitat (EFH) and the Fisheries Ecosystem Plan (FEP), the SAFMC contracted the Florida Fish and Wildlife Research Institute (FWC-FWRI) in 2012 to create a database called Ecospecies (http://saecospecies.azurewebsites.net/). Major components of the Gray Snapper (Lutjanus griseus) species life history (SLH) include the following: Taxonomy, Geographic Range, Benthic Habitat, Water Column Habitat, Artificial Reefs, Shrimp Trawl Bycatch, Food Habits, Reproduction, Growth, Value and Status, Stock Enhancement, Population, Management Regulations, Ecological Interactions, and Human Impacts. Citations and references are available for each entry in the Ecospecies database. Almost everything published concerning this species is reviewed in the present SLH profile.
... Previous studies on juvenile grey snapper (L. griseus) have found that growth efficiencies decrease at higher salinities 25 and laboratory experiments have shown that they prefer lower salinities that minimize osmoregulatory costs 26 . Juvenile turbot (Scophthalmus maximus) have also shown better food conversion efficiencies at lower salinity levels 27 , so juveniles of mangrove jack might respond in similar ways to changes in salinity from increased rainfall. ...
... Juvenile turbot (Scophthalmus maximus) have also shown better food conversion efficiencies at lower salinity levels 27 , so juveniles of mangrove jack might respond in similar ways to changes in salinity from increased rainfall. Additionally, there might be indirect effects of salinity in estuarine habitats such as salinity-induced changes to prey, predator or competitor abundances 26 . ...
Many marine fishes have life history strategies that involve ontogenetic changes in the use of coastal habitats. Such ontogenetic shifts may place these species at particular risk from climate change, because the successive environments they inhabit can differ in the type, frequency and severity of changes related to global warming. We used a dendrochronology approach to examine the physical and biological drivers of growth of adult and juvenile mangrove jack (Lutjanus argentimaculatus) from tropical north-western Australia. Juveniles of this species inhabit estuarine environments and adults reside on coastal reefs. The Niño-4 index, a measure of the status of the El Niño-Southern Oscillation (ENSO) had the highest correlation with adult growth chronologies, with La Niña years (characterised by warmer temperatures and lower salinities) having positive impacts on growth. Atmospheric and oceanographic phenomena operating at ocean-basin scales seem to be important correlates of the processes driving growth in local coastal habitats. Conversely, terrestrial factors influencing precipitation and river runoff were positively correlated with the growth of juveniles in estuaries. Our results show that the impacts of climate change on these two life history stages are likely to be different, with implications for resilience and management of populations.
... Although limited in spatial extent, the future reduction in salinity and salinity variation, particularly during future dry seasons, may locally impact resident species (e.g., clown goby, goldspotted killifish, rainwater killifish). Previous research in Florida Bay or nearby estuaries support the findings of a negative association with salinity of bay anchovy and Eucinostomus species (Johnson et al. 2002), positive associations with salinity of pinfish (Johnson et al. 2002;Kearney et al. 2015), gray snapper (Serrano et al. 2010), and gulf toadfish (Ley et al. 1999), and associations with a mesohaline to polyhaline range of salinity by spotted seatrout (Rutherford et al. 1989;Powell 2003;RECOVER 2017). Previous studies support salinity variation as a driver in Florida Bay, finding a similarly circumscribed distribution of clown goby in areas with high salinity variability within northeastern Florida Bay (Flaherty et al. 2013). ...
Predicting future changes in species distributions due to climate change and sea-level rise are critical for informing adaptive management of large-scale estuarine ecosystem restorations. In this study, we used binomial generalized additive models (GAMs) to predict suitable habitat for 24 species groups under current conditions and projected conditions for 2060 in Florida Bay, a large and shallow estuary subject to one of the largest hydrological restoration efforts in the world, the Comprehensive Everglades Restoration Plan (CERP). Overall, potential sea-level rise due to climate change had a large influence in the system, driving the biggest reduction in habitat suitability in both magnitude and spatial extent. In contrast, the impacts of increased freshwater flows (and localized changes in salinity and salinity variation) from restoration influenced a greater number of species, but are predicted to have a relatively smaller influence on future habitat suitability for the majority of species in Florida Bay. The broadest positive changes in occurrence probabilities were found for spotted seatrout, pink shrimp, hardhead halfbeak, scaled sardine, common snook, and great barracuda. Negative changes occurred in numerous small-bodied species such as hardhead silverside, goldspotted killifish, rainwater killifish, and bay anchovy, as well as larger-bodied Crevalle jack, gray snapper, and white mullet. The model results predicted winners and losers, thereby providing an opportunity to ensure management strategies are designed appropriately to best achieve the desired results for the future of the Florida Bay ecosystem.
... Methods, such as counter-current troughs, Y-mazes, and shuttle box systems have been used to assess fish behaviour in relation to conspecific recognition, environmental pressures, and preference for chemical cues, such as toxins and chemoattractants [36][37][38][39][40][41][42][43] . These systems are potentially simple to build and can produce natural cue gradients, however they offer poor control of cue plumes and the movement of response animals is often restricted 44 . ...
Characterising crustacean behaviour in response to conspecific chemical cues contributes to our evolving knowledge of the drivers of their social behaviour. There is particular interest in understanding the chemical and behavioural mechanisms contributing to cannibalism at ecdysis, as this behaviour substantially limits culture productivity of several commercially important crustaceans. Before investigating the role of chemoreception in cannibalism of moulting crustaceans, we must investigate its role in detecting moulting conspecifics. Here we use a two-current choice flume to observe juvenile tropical rock lobster (Panulirus ornatus) behavioural response to conspecific moulting cues and identifying attracted and avoidant behaviours correlating to moult stage and social relationship. Observed cue preferences show inter-moult juveniles are attracted to the moulting cues of lobsters to which they are socially naïve. In contrast, post-moult and inter-moult juveniles avoid the moulting cues of individuals whom they are socially familiar with. Average speed and total distance travelled by lobsters increases in response to conspecific moulting cues. This study demonstrates the suitability of a two-current choice flume for behavioural assays in P. ornatus and characterises clear behavioural patterns in juveniles exposed to conspecific moulting cues. This provides important framework for understanding the role of chemical communication in eliciting cannibalism.
... On a more temporal basis, reefs in some areas (e.g., Kaneohe Bay, Hawai'i) can succumb to storm flooding and freshwater inundation, making for hyposaline challenges and even mortality for resident fish species ( Jokiel et al., 1993). Mechanistic studies (e.g., in the economically valuable coral trout, P. maculatus and Plectropomus leopardus, and also associated with capture stress; Frisch and Anderson, 2005) have been done including determining salinity preference (Serrano et al., 2010) and understanding the role of salinity in modulating reproductive hormones (Hung et al., 2010) and stress (e.g., heat shock proteins and cytoprotection; Tang et al., 2014a). In many cases, changes in gill morphology are observed, sodium potassium pump (Na + , K + , ATPase) activities and Na + , K + , 2Cl À cotransporter proteins are measured and/or isoforms assessed to determine a coral reef fish's status in hypo-or hyper-saline conditions (Tang et al., 2014b). ...
Coral reef fishes and the ecosystems they support represent some of the most biodiverse and productive ecosystems on the planet yet are under threat as they face dramatic increases in multiple, interacting stressors that are largely intensified by anthropogenic influences, such as climate change. Coral reef fishes have been the topic of 875 studies between 1979 and 2020 examining physiological responses to various abiotic and biotic stressors. Here, we highlight the current state of knowledge regarding coral reef fishes' responses to eight key abiotic stressors (i.e., pollutants, temperature, hypoxia and ocean deoxygenation, pH/CO2, noise, salinity, pressure/depth, and turbidity) and four key biotic stressors (i.e., prey abundance, predator threats, parasites, and disease) and discuss stressors that have been examined in combination. We conclude with a horizon scan to discuss acclimation and adaptation, technological advances, knowledge gaps, and the future of physiological research on coral reef fishes. As we proceed through this new epoch, the Anthropocene, it is critical that the scientific and general communities work to recognize the issues that various habitats and ecosystems, such as coral reefs and the fishes that depend on and support them, are facing so that mitigation strategies can be implemented to protect biodiversity and ecosystem health.
... For aquatic species, experimental devices are all based on the same principle(Jutfelt et al., 2017): a shuttle tank allowing animals to choose between two (or more) water currents with distinct properties (substrate, odor, color, physicochemical properties). Choice tests can evaluate single or combined preferences with various sensory modalities (vision, smell, taste) and on multiple species from fish to coral larvae and including molluscs (fish:Serrano et al., 2010; corals larvae: ...
En France la seiche commune Sepia officinalis est élevée en eau claire alors qu’elle a évolué dans un environnement naturel où la turbidité de l’eau varie saisonnièrement et quotidiennement. Cette thèse tente de voir si l’élevage dans des conditions proches du milieu naturel (i.e turbides) ne permet pas d’améliorer les conditions de vie des seiches en laboratoire. Nous avons démontré que la préférence pour le milieu turbide est âge dépendante : les jeunes seiches préfèrent l’eau claire et les plus âgées l’eau turbide. Le comportement prédateur des seiches n’est pas modifié en milieu turbide sauf pour le groupe élevé en turbidité forte où le comportement prédateur est moins performant en eau turbide. Les seiches adaptent leur camouflage à la turbidité de l’eau de leur environnent. L’environnement d’élevage joue probablement sur la façon dont les seiches perçoivent la turbidité. La turbidité impacte également l’ensablement, un comportement défensif pourtant peu dépendant des stimuli visuels. Nous avons également montré un effet de l’expérience individuelle et du milieu d’élevage sur l’adaptation à la turbidité. A l’âge de 7 jours les seiches élevées dans une eau turbide développent des capacités visuelles supérieures en eau claire (sensibilité à la polarisation) et en eau turbide (contraste d’intensité). Nos résultats préliminaires semblent suggérer que la seiche utilise préférentiellement la modalité olfactive en eau turbide. La couleur de l’œuf, le site de ponte et le milieu d’élevage influencent les capacités visuelles de seiches juvéniles et conditionnent leur sensibilité et leur adaptation à la turbidité. Chez une espèce d’eau claire, Sepia pharaonis la turbidité influence les capacités visuelles mais les individus semblent limités dans les réponses adaptatives qu’ils peuvent produire pour se camoufler dans un milieu turbide. L’ensemble de nos résultats montrent que la turbidité du milieu, lorsqu’elle est modérée, est un élément d’enrichissement qui pourrait être utilisée afin d’améliorer les conditions d’élevage de la seiche commune.
... There is some evidence that Delta Smelt exhibit shoaling behavior 43 , so three replicates of ten fish per replicate were used during each preference trial to test their volitional movements in the shuttlebox apparatus. Most similar studies have examined the behavioral responses of a single fish to different levels of an environmental stimulus [44][45][46][47] , rather than the multiple fish used here. Delta Smelt were not fed during the preference trials-which lasted up to six days-to avoid introducing any factors that could elicit a preference for a particular side of the shuttlebox. ...
Temperature and salinity often define the distributions of aquatic organisms. This is at least partially true for Delta Smelt, an imperiled species endemic to the upper San Francisco Estuary. While much is known about the tolerances and distribution of Delta Smelt in relation to these parameters, little is known regarding the temperature and salinity preferences of the species. Therefore, the temperature and salinity preferences of sub-adult Delta Smelt were investigated across a wide range of thermal (8–28 °C) and salinity (0–23 ppt) conditions. Replicates of ten fish were allowed to swim between two circular chambers with different temperature or salinity, and the distribution of fish between the chambers was recorded. We found that Delta Smelt showed no temperature preference below 15 °C, a modest aversion to the warmer tank from 15 to 28 °C, and a strong aversion to the warmer tank with elevated mortality at temperatures above 28 °C. Delta Smelt also preferred lower salinities, and this preference became more pronounced as salinity increased toward 23 ppt. These results indicate that Delta Smelt can tolerate high temperatures and salinities for a short time, and that their preferences for lower temperature and salinity strengthens as these variables increase.
... Preferred salinity was calculated as the median salinity individual fish experienced at all time points throughout the 4-h experiment (Schurmann et al. 1991;Serrano et al. 2010;Christensen et al. 2021). Prior to experimentation, fish were placed into the shuttle box for 24 h to acclimate. ...
Within Salmonidae, spawning and rearing in brackish water is rare; however, brackish-water resident lake trout (Salvelinus namaycush) have recently been documented in the Arctic. Additionally, early rearing in brackish-water environments increased the fish’s ability to ionoregulate in elevated salinities. Here, we examined the impact of a freshwater (FWR, 0 ppt) or brackish-water (BWR, 5 ppt) rearing environment on salinity preference in lake trout using a dynamic choice experiment. We observed significant differences in salinity preference between our treatments suggesting the importance of early environment in shaping salinity preference. Contrary to our predictions, FWR lake trout selected higher salinity (17.3 ppt) compared to BWR fish (4.8 ppt). Four of the seven FWR fish had preferred salinities near 30 ppt, which is considered physiologically challenging and potentially lethal for lake trout based on direct transfer experiments. Thus, heightened FWR salinity preference might not be a true preference but rather due to a reduced ability to sense differences in salinity, and a result of chance as mean preferred salinity was near half that of the upper and lower thresholds, and variance was larger. Selection of lower salinity by BWR fish suggests that the ability to sense and select different salinities is present in lake trout as a species and appears to be linked to difference in early rearing at elevated salinities.
... Ambient air was bubbled into the novel chamber. The mirrored water circulation of the two chambers minimized water exchange across the connecting channel but still allowed for fish to leave the occupied chamber to the novel chamber (Serrano et al. 2010). We defined a fish to have left the home chamber once its body had passed the halfway line of the connecting channel. ...
Biological invasions erode ecosystem functioning and occur more frequently in freshwater ecosystems than terrestrial environments. Non‐physical deterrents may be used to limit invasive fish dispersal without altering the streamflow or connectivity of a watershed. Little is currently known about how behavioural variation among individuals may effect deterrent efficacy, although such variation has been shown to affect fish dispersal in other contexts, such as range expansion. Furthermore, deterrent effectiveness is rarely tested when fish are motivated to disperse. Across a control, CO2, and CO2 + deterrent treatment, we quantified the avoidance response of invasive Common Carp (Cyprinus carpio) to a combined acoustic‐stroboscopic deterrent. In the CO2 treatment, we motivated individuals to enter a novel environment by degrading the home chamber of a choice arena with a continuous infusion of CO2. In the CO2 + deterrent treatment we introduced acoustic and stroboscopic stimuli to delay fish departure and evaluate deterrent efficacy. Finally, we tested a subset of the fish multiple times to determine if fish consistently responded to the same concentration of CO2. We found that the acoustic and stroboscopic stimuli could detain fish in an increasingly unfavorable environment. Common Carp only took 195 and 131 seconds to swim between chambers during the control and CO2 treatment, but took an average of 596 seconds in the CO2 + deterrent treatment. High CO2 concentrations in the CO2 + deterrent treatment led to most fish eventually dispersing towards the deterrent stimuli. Avoidance behaviour varied widely within the CO2 + deterrent treatment, and Common Carp expressed repeatable differences in the tank‐inflow CO2 concentrations observed during chamber departure. Such inter‐individual variation in deterrent avoidance indicates that some individuals within a given species are more likely to move past a deterrent than others.
... Although neither salinity nor temperature acted as a major determinant of suitability, these variables acted as filters to mediate the relative suitability of otherwise similar habitats. Previous research has demonstrated significant inter-species variation in salinity tolerances, with L. griseus being abundant in low-to-intermediate salinities and H. sciurus being abundant in stable, high salinities [53,100]. These relationships were reflected in MaxEnt's predictions and were especially noticeable in Biscayne Bay, where salinity fluctuates significantly as a result of both freshwater discharge and tidal exchange. ...
Coastal habitats have experienced significant degradation and fragmentation in recent decades under the strain of interacting ecosystem stressors. To maintain biodiversity and ecosystem functioning, coastal managers and restoration practitioners face the urgent tasks of identifying priority areas for protection and developing innovative, scalable approaches to habitat restoration. Facilitating these efforts are models of seascape connectivity, which represent ecological linkages across heterogeneous marine environments by predicting species-specific dispersal between suitable habitat patches. However, defining the suitable habitat patches and migratory pathways required to construct ecologically realistic connectivity models remains challenging. Focusing on two reef-associated fish species of the Florida Keys, United States of America (USA), we compared two methods for constructing species- and life stage-specific spatial models of habitat suitability—penalized logistic regression and maximum entropy (MaxEnt). The goal of the model comparison was to identify the modeling algorithm that produced the most realistic and detailed products for use in subsequent connectivity assessments. Regardless of species, MaxEnt’s ability to distinguish between suitable and unsuitable locations exceeded that of the penalized regressions. Furthermore, MaxEnt’s habitat suitability predictions more closely aligned with the known ecology of the study species, revealing the environmental conditions and spatial patterns that best support each species across the seascape, with implications for predicting connectivity pathways and the distribution of key ecological processes. Our research demonstrates MaxEnt’s promise as a scalable, species-specific, and spatially explicit tool for informing models of seascape connectivity and guiding coastal conservation efforts.
... To conclude, two-channel choice chambers are incapable of producing non-mixed flows when using water masses of different densities. We thus suggest that Baptista and colleagues redo tests III and IV using other methods, such as a shuttle box system (Serrano et al. 2010), and publish a correction to their paper accordingly. We sincerely hope that the authors of Baptista et al. (2020) and other readers find this correspondence constructive, and that our advice on how to ensure quality control and replicability will be helpful for future research. ...
Two-channel choice chambers are a common tool for testing preference or avoidance of aquatic organisms to a range of chemical cues and environmental parameters, including habitat cues. If used correctly, they produce two parallel, non-overlapping, laminar water currents in which the animal can swim freely and choose between the currents, that in chemosensory terms are, for example, representative of two different habitats. In a recent paper, using a two-channel choice chamber, Batista et al. (2020, Behavioral Ecology and Sociobiology 74:67) investigated the response of white seabream towards several habitat and environmental cues including elevated water temperature and reduced salinity. The authors concluded that white seabream had no preference for any of the stimuli presented and hypothesised that other mechanisms are responsible for habitat selection in this species. The choice chamber methodology used, however, had several fundamental problems that most likely confounded the results. Given that the water masses used simultaneously on each side of the chamber differed in salinity and temperature, they also differed in density, inevitably resulting in water mixing. The currents in the chamber, therefore, could have not met the methodological prerequisites of parallel laminar and non-overlapping flows, making attribution of the fish to either water mass impossible. While stressing that two-channel choice chambers are incapable of producing non-mixed flows when using water masses of different densities, this correspondence provides recommendations on how to overcome this problem using a different methodology. Advice is also given on how to avoid similar methodological problems in future studies, to increase quality control and transparency and ensure replicability of studies using two-current choice chambers.
... Salinity gradients can act as important abiotic cues for marine larvae to locate coasts, estuaries and rivers, especially for diadromous species (Kingsford et al. 2002, Goldstein & Butler 2009, Serrano et al. 2010. Climate change is forecast to result in more variable precipitation patterns, as well as overall increases or decreases (depending on location and season) in total annual precipitation (Zhang et al. 2007), with direct consequences for estuarine and near-shore seawater salinity (Durack et al. 2012) through altered runoff, flooding and river flow regimes (Figure 1). ...
... For juvenile emperors from the lagoon, the overall more negative d 18 O otolith values in juvenile fish collected in January may reflect the influence of changing water composition during the NEM season, due to the input of fresh water from precipitation and tributaries potentially affecting isotope signatures of water in the lagoon (Cocheret de la Morinière et al. 2003). Furthermore, the effects of unfavourable environmental conditions during peak rainfall in the NEM may force the juvenile reef fish to emigrate or to go deeper in the lagoon because they may have certain salinity tolerances and preferences (Estudillo et al. 2000;Serrano et al. 2010). Unlike d 18 O otolith , a small variation in d 13 C otolith between seasons may not only reflect a change in water composition, because d 13 C otolith values can be affected by several factors (see above), but may also be related to differences in metabolic rates due to seasonal temperature changes (Kalish 1991;Trueman et al. 2016). ...
Stable isotope analyses of muscle tissue (δ13Cmuscle and δ15Nmuscle) and otoliths (δ13Cotolith and δ18Ootolith) were used to retrospectively track habitat uses of Lethrinus lentjan, and to determine any association between Setiu Lagoon (nursery habitat) and coastal artificial reefs (CARs; adult habitats) on the Terengganu coast, Malaysia. Muscle stable isotopes exhibited a spatial change from inshore to offshore habitats associated with growth, possibly related to the reef-ward movement of the fish. Otolith stable isotopes of adult fish from CARs were measured in juvenile (from outside the core to the first opaque zone of otolith) and adult (the edge of otolith) portions and were compared with those of juveniles from Setiu Lagoon, suggesting that the adult fish may not primarily use the lagoon as a nursery before ontogenetically migrating to CARs. The effects of coastal currents between monsoonal seasons could reorientate offshore juvenile migration; hence, adult cohorts in CARs may be replenished from various nursery habitats along the coast. Additionally, similarities in the δ18Ootolith values of juvenile and adult sections suggested that some individuals may not spend their juvenile phases in shallow estuarine habitats. Based on the findings of this study, we recommend that coastal conservation strategies take into account multiple nursery habitats rather than a single one.
http://www.publish.csiro.au/MF/MF18302
... Prior to commencing the experiments, perch for this experiment were captured using a beach seine in the Northern part of the Curonian Lagoon at the same place and time as those perch which were used for growth experiments and were acclimated to laboratory conditions as described above. Two types of behavioural experiments were performed to assess perch response to (1) salinity gradient (freshwater vs salinity 6) and (2) different temperature regimes (18°C vs 12°C) in shuttle tank system (Fig. 2), which is a modification of the device described by Schurmann et al. (1991) and Serrano et al. (2010). The 8shaped shuttle box system maintains different constant water salinity or temperature in each of the chambers. ...
Climate change is likely to increasingly impact estuarine fish populations. Changes in water temperature or salinity can have deleterious effects on fish growth and behaviour. A decrease in the abundance of freshwater fish in the northern areas of the Curonian Lagoon has been attributed to increased salinity of inflowing water from the Baltic Sea. Thus, this study investigated the effects of possible changes in environmental salinity and temperature on the growth and behaviour of perch (Perca fluviatilis L.). Laboratory experiments revealed that brackish water (salinity 3 and 6) has neither a negative nor a positive effect on growth rates among perch young-of-the-year, when compared to freshwater (salinity 0). In contrast, results from behavioural experiments demonstrated that perch prefer to remain in brackish water (salinity 6) when given a choice between brackish and freshwater, and in warm water (18 °C) when given a choice between warm and cold water (12 °C). For this reason, the temperature rather than the salinity of inflowing colder brackish water from the Baltic Sea will be the most likely driver of short-term changes in fish distribution in the Curonian Lagoon.
... Thus, two-current choice flumes are not suitable for testing the behavioural choices of aquatic animals using water currents of anything other than very minor differences in temperature and/or salinity and alternative methods [e.g. shuttle box or annular preference chamber (Myrick et al. 2004;Serrano et al. 2010)] should be considered. As a result, unfortunately, two-current choice flumes are likely to be of limited value for testing temperature or salinity preferences since the conditions which can be presented to animals in these chambers will have little relevance to those that the animals find in nature. ...
Two-current choice flumes are used to measure preference and avoidance behaviour in response to chemical cues in aquatic animals. If used correctly, they produce two parallel, non-overlapping, laminar water currents in which the animal can move freely and choose between the two currents. As climate change is affecting water temperature, and altered precipitation patterns are changing water salinity, two-current choice flumes are increasingly being used to test the choice between water currents of different temperatures and salinities. This inevitably means that water currents of different densities are being used simultaneously in the flume. Here, we investigated the tolerance range for density differences due to temperature and salinity in five common flume designs. Through dye tests and stepwise modifications of temperatures and salinities we determined the limits for laminar and non-overlapping flows. We also developed an automated method for quantifying the overlap precisely and objectively. The tolerance for density differences between the water currents where laminar and non-overlapping flows were maintained was surprisingly low, withstanding ± 0.5 °C temperature differences, and ± 0.1 PSU salinity differences, i.e. a maximum density difference of 0.28 gL⁻¹. Above these very narrow limits we found a range where the flumes showed partly overlapping, stratified water currents that preclude easy determination of cue preference. We conclude that two-current choice flumes are not suitable for testing the behavioural choices of aquatic animals using water currents of anything other than minor differences in temperature and/or salinity.
... Most fish species survive in a narrow range of pH and salinity. Any deviation from the optimal range of pH or salinity or both can disrupt their physiological functions (Whitney et al., 2016;Mubarik et al., 2015;Serrano et al., 2010), eventually, alter their life history traits such as growth (Ong et al., 2015) and reproduction (Kwong et al., 2014). ...
... Most fish species survive in a narrow range of pH and salinity. Any deviation from the optimal range of pH or salinity or both can disrupt their physiological functions (Whitney et al., 2016;Mubarik et al., 2015;Serrano et al., 2010), eventually, alter their life history traits such as growth (Ong et al., 2015) and reproduction (Kwong et al., 2014). ...
Variation in pH (acidification) and salinity conditions have severe impact at different levels of biological organization in fish. Present study focused to assess the effects of acidification and salinity changes on physiological stress responses at three different levels of function: i) hormonal and oxidative response, ii) osmoregulation and iii) reproduction, in order to identify relevant biomarkers. Second objective of the study was to evaluate the efficacy of plant (Mucuna pruriens) extract for alleviating pH and salinity related stress. Guppies (Poecilia reticulata) were exposed to different pH (6.0, 5.5, 5.0) and salinity (1.5, 3.0, 4.5 ppt) for 7, 14 and 21 days. Following exposure to stress for respective duration, fish were fed diet containing methanol extract of Mucuna seeds (dose 0.80 gm/kg feed) for 7, 14 and 21 days to measure their possible recovery response. Stress hormone (cortisol), hepatic oxidative stress parameters [superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GRd), glutathione peroxidise (GPx), glutathione S-transferase (GST), malondialdehyde (MDA), glutathione (GSH)], gill osmoregulatory response (Na+-K+ATPase activity), sex steroid profiles and mating behaviours (gonopodial thrust and gestation period) were estimated. Cortisol and MDA levels increased with dose and duration of acid and salinity stress, and cortisol levels were higher in males than in females. Effect on Na+-K+ATPase activity was more intense by salinity stress rather than pH induced stress. Both acid and salinity stress reduced sex steroid levels, and mating response was highly affected by both stresses in a dose- and duration-dependent manner. Mucuna treatment reduced stress-induced alteration of cortisol, MDA, Na+-K+ATPase activity and reproductive parameters. Dietary administration of Mucuna seed extract decreased the intensity of environmental stressors at all three functional levels. Mucuna treatment was more effective against salinity stress than acid stress. Thus, cortisol, oxidative stress marker MDA and Na+-K+ATPase could be effective indicators for acid and salinity stress in wild and domestic fish populations. Dietary administration of Mucuna extract may limit the detrimental effects of acidification and salinity variations that are the inevitable outcomes expected under global climate change conditions
... Salinity has previously been shown to induce behavioral changes in a number of euryhaline species (Swanson, 1998;Edeline et al., 2005;Tietze and Gerald, 2016). Contrary to our results, most studies demonstrate a negative correlation between activity level and increasing salinity in aquatic organisms (e.g., Edeline et al., 2005;Serrano et al., 2010). The increase in activity observed in K. marmoratus could represent a behavioral escape mechanism to seek out more favorable microhabitats. ...
Amphibious fishes moving over land between aquatic habitats likely encounter abrupt changes in a number of environmental conditions, including salinity. This study characterized the 1) spatial heterogeneity in salinity in the mangrove forest habitat of the self-fertilizing, amphibious mangrove rivulus (Kryptolebias marmoratus), 2) metabolic cost and behavioral response to acute exposure to novel salinity, and 3) repeatability of individual responses to acute changes in salinity. In mangrove habitats on Long Caye, Belize, salinity varied widely over short distances from 20.9-41.7‰ over a 90 cm distance. In the lab, fish were exposed to an acute change in salinity of Δ10, 20, or 30‰. Oxygen consumption significantly decreased in response to a 10‰ decrease in salinity and increased when salinity was elevated by 30‰. Activity levels significantly increased with an increase in salinity (Δ20 and 30‰). Individuals showed repeatable differences in both oxygen consumption rates and activity levels. Together, our data show that K. marmoratus is highly responsive to abrupt increases in salinity. Thus, movements made by K. marmoratus between temporary pools in the mangrove forest will acutely alter behavior and possibly metabolism, with many potential ecological consequences. © 2018 by the American Society of Ichthyologists and Herpetologists.
... The optimal salinity varies considerably among both stenohaline and euryhaline species, indicating that other factors than ion-regulation, such as hormone levels and hormonal control in relation to osmoregulation (Morgan & Iwama, 1996), can influence the whole-animal energetic response to salinity. Compared with studies on the effect of salinity on whole-animal energetics, only few studies have concerned the behavioural salinity preference of fish in laboratory settings where salinity has been set as the only varying factor (McInerney, 1964;Serrano et al., 2010;Bucking et al., 2012). Most teleosts have only limited scope for coping with varying salinities (Evans, 1984) and behavioural salinity preference could differ among species. ...
The present study determined the behavioural salinity preference of a freshwater stock of juvenile yellow perch Perca flavescens acclimated to salinities of 0 and 10. The preferred salinities ranged between 7·3 and 13·0 (mean ± s.d. = 10·4 ± 1·7; n = 13) with no significant effect of acclimation salinity. The results showed that juvenile P. flavescens prefers near isoosmotic salinities, which could be due to a lowered energetic cost of osmoregulation.
... These larvae would stay on the side of the shuttle box they were placed in until the experiment ended, regardless of the length of the experiment. Similar behavior has been observed in subadult Lutjanus griseus inside of a shuttle box designed to investigate salinity preference 51 . Some Gerreidae and Clupeidae larvae, on the other hand, would energetically swim into the nearest wall as soon as they were placed into the shuttle box. ...
Transport of coral reef fish larvae is driven by advection in ocean currents and larval swimming. However, for swimming to be advantageous, larvae must use external stimuli as guides. One potential stimulus is “odor” emanating from settlement sites (e.g., coral reefs), signaling the upstream location of desirable settlement habitat. However, specific chemicals used by fish larvae have not been identified. Dimethyl sulfide (DMS) is produced in large quantities at coral reefs and may be important in larval orientation. In this study, a choice-chamber (shuttle box) was used to assess preference of 28 pre-settlement stage larvae from reef fish species for seawater with DMS. Swimming behavior was examined by video-tracking of larval swimming patterns in control and DMS seawater. We found common responses to DMS across reef fish taxa - a preference for water with DMS and change in swimming behavior - reflecting a switch to “exploratory behavior”. An open water species displayed no response to DMS. Affinity for and swimming response to DMS would allow a fish larva to locate its source and enhance its ability to find settlement habitat. Moreover, it may help them locate prey accumulating in fronts, eddies, and thin layers, where DMS is also produced.
... For instance, the spontaneous swimming speed of grey snapper Lutjanus griseus (L. 1758) was <0·5 L B s −1 (Serrano et al., 2010), Adriatic sturgeon Acipenser naccarii Bonaparte 1836 at 0·5 L B s −1 (McKenzie et al., 1995) and seabream Sparus aurata L.1758 at 0·5 L B s −1 (Steinhausen et al., 2010). The spontaneous swimming speed of one M. anguillicaudatus relative to L T exceeded these other species, perhaps because all these species are generally larger than M. anguillicaudatus used in the present study. ...
Experiments on the swimming kinetics and behaviour of weather loach Misgurnus anguillicaudatus showed that horizontal swim speed was significantly greater than swim speeds when ascending to or descending from the water surface to gulp air. Vertical swimming speeds during ascending or descending were similar. Misgurnus anguillicaudatus swam unsteadily during vertical movements compared with horizontal movements.
... Indeed, the catadromous cobia, Rachycentron canadium, are resistant to forecasted rises in CO 2 in traits such as growth, development, swimming ability and swimming activity (Bignami et al. 2013). Because of their developmental shifts between marine and freshwater environment, such species are responsive to changes in water temperature and salinity (Edeline et al. 2006;Serrano et al. 2010), but we do not know whether the preferences for these cues can be affected by ocean acidification. ...
Ocean acidification alters the way in which animals perceive and respond to their world by affecting a variety of senses such as audition, olfaction, vision and pH sensing. Marine species rely on other senses as well, but we know little of how these might be affected by ocean acidification. We tested whether ocean acidification can alter the preference for physicochemical cues used for dispersal between ocean and estuarine environments. We experimentally assessed the behavioural response of a larval fish (Lates calcarifer) to elevated temperature and reduced salinity, including estuarine water of multiple cues for detecting settlement habitat. Larval fish raised under elevated CO2 concentrations were attracted by warmer water, but temperature had no effect on fish raised in contemporary CO2 concentrations. In contrast, contemporary larvae were deterred by lower salinity water, where CO2-treated fish showed no such response. Natural estuarine water—of higher temperature, lower salinity, and containing estuarine olfactory cues—was only preferred by fish treated under forecasted high CO2 conditions. We show for the first time that attraction by larval fish towards physicochemical cues can be altered by ocean acidification. Such alterations to perception and evaluation of environmental cues during the critical process of dispersal can potentially have implications for ensuing recruitment and population replenishment. Our study not only shows that freshwater species that spend part of their life cycle in the ocean might also be affected by ocean acidification, but that behavioural responses towards key physicochemical cues can also be negated through elevated CO2 from human emissions.
... The anadromous nature of the Arctic charr, where the species experiences different salinities at different life stages, highlights a different problem in assessing impacts of climatic change on the species, being the effect of salinity. It has been shown that fishes are capable of choosing a saline environment (Serrano et al. 2010), as well as expressing migratory behavior suggested to relate to the scope for activity (Christensen et al. 2016). Thus, whether the whole scope for activity is shifted (different T opt ) or compressed (same T opt ) on a thermal scale, with changes in salinity, at different life stages should be a goal for future research. ...
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Assessment of maximum aerobic scope, as a proxy for scope of activity, in ectotherms can be instrumental in predicting distributional responses to e.g. global warming. The waters of the Arctic regions represent one of the most vulnerable ecosystems to climate change. In this study, we determine the optimum temperature (Topt) of nine adult Arctic charr (Salvelinus alpinus) from Qeqertarsuaq, Greenland, using maximum heart rate (fHmax) for investigating the optimal temperatures for activity. The Arrhenius breakpoint of maximum heart rate measurements occurred between 5.9 and 8.3 °C (average = 7.5 °C ± 0.4). The Q10 breakpoint occurred at an average of 7.1 °C ± 0.3. There was no significant difference between the breakpoint temperature found using Q10 and Arrhenius [two-sample t test, df = 16; p > 0.1]. The highest fHmax was found at 12.8 °C ± 1.0 reaching an average of 61.8 BPM ± 3.1. Arrhythmia occurred between 11 and 18 °C (average = 15.2 °C ± 0.9). The results obtained in this study suggest that the studied population of Arctic charr lives at summer temperatures (−0.6 to 9.1 °C) that are optimal for activity, but an increase in temperature expected with climate change, could have an impact on life cycle events and fitness-related tasks for this northern population.
... Terrigenous allochthonous material is one of the most important sources of nutrients for primary and secondary productivity in the neritic zone (Polis and Hurd 1996), and contributes to enhancing the overall productivity of these systems (Maslowski 2003). Studies have shown that changes in the riverine input can affect individual species as well as entire communities (Serrano et al. 2010;Olin et al. 2013). ...
The Thukela Bank, KwaZulu-Natal, supports a diverse ecosystem and South Africa’s only prawn fishery. Oceanographic studies suggest riverine input is not important for the biology of this system, whereas biological studies suggest the contrary, with prawn catches increasing with increased fluvial run-off. The aim of this study was to determine (i) the importance of riverine and marine organic matter for the Thukela Bank food web; and (ii) whether there are seasonal changes in the Thukela River stable isotope values, and, if so, whether these are reflected in the isotope values of demersal organisms. Estuarine organic matter, sediments and demersal organisms were collected from several sites across the bank in the wet and dry seasons of 2008, 2009 and 2010. Marine particulate organic matter was also collected in 2010 and analysed for δ13C and δ15N, as well as C/N ratios. There were strong seasonal changes in isotopic values of organic matter and fauna, especially faunal δ13C. There was an apparent time-lag in organisms assimilating riverine organic matter isotopic values, with the isotopic signature of demersal organisms reflecting that of riverine organic matter from the previous season, which is likely the result of tissue turnover time. In 2010, Thukela Bank sediment organic matter was of riverine origin and this maintained the demersal food web. We conclude that Thukela River organic matter is an important input to the food web of the Thukela Bank, indicating that any future damming of the catchment area could have serious consequences for this ecosystem.
... The 'shuttlebox' system (Loligo Systems, Inc.) used to test salinity choice by S. salar smolts in the laboratory was previously described by Serrano et al. (2010), with minor modifications (e.g., smaller tank size and tubing) during the present study ( Figure 5.1). The choice tank consisted of two circular compartments, each of 41 cm diameter and 19 cm depth. ...
Atlantic salmon Salmo salar populations are diminished throughout their range and high marine mortality is among the drivers of the failure of many stocks to recover. A goal of salmon recovery is to maximize the number of juvenile ‘smolts’ entering the ocean to offset loss therein. Dam removals and changes to hydropower allocation in Maine’s largest river, the Penobscot River, have occurred as part of the Penobscot River Restoration Project (PRRP). These activities, in addition to stocking have the potential to influence the number of smolts reaching the ocean. Telemetry was used to investigate factors influencing initiation of migratory behavior, movement rates, migratory route, and survival through freshwater (FW) before and after changes to the system resulting from the PRRP, and behavior and survival of smolts during estuary migration.
Initiation of migration was influenced by smolt development, stocking location and environmental conditions. Smolts with the greatest gill Na+, K+-ATPase activity (physiological development) initiated migration 24 hours sooner than fish with the lowest gill NKA activity. Fish with the greatest cumulative temperature experience (accumulated thermal units: ATU) initiated migration 5 days earlier than those with lowest ATU. Smolts released furthest upstream initiated migration earlier than those released downstream, and movement rate increased 5-fold from upstream to the estuary. Movement rate increased from 2.8 km·h-1 to 5.4 km·h-1 in reaches where dams were removed, and decreased from 2.1 km·h-1 to 0.1 kmh-1 after powerhouse construction.
Proportional use of the Stillwater Branch was low (0.12, 95% CI = 0.06 – 0.25), and survival through the dams therein was relatively high (0.99) prior to installation of new powerhouses, decreasing slightly thereafter. Survival at Milford Dam, now the lowermost dam in the main-stem, was low (0.91) prior to increased power generation, whereas survival at Great Works and Veazie Dams was high (0.99 and 0.98) prior to removal. Survival was higher through free-flowing reaches (> 0.99·km-1) than reaches containing dams (c. 0.95·km-1). Survival was reduced at high (> 2000 m3s-1) or low (
... Stewar-Fielder et al. (2005) y Castillo- Vargasmachuca et al. (2013), y en otras especies de pargos, mientras que en temperaturas menores a 24°C disminuyeron su crecimiento, sin afectar la supervivencia. Serrano et al. (2010) encontraron que el pargo gris L. griseus en condiciones de laboratorio, prefiere salinidades intermedias en el rango de 9-23 y en salinidades extremas reduce su actividad en compensación del mayor gasto energético por osmorregulación. Los resultados de este experimento mostraron que de 86,8 a 90,0% de los juveniles de pargo lunarejo, sin exposición previa a la salinidad, fueron capaces de sobrevivir a una transferencia directa de salinidad 15 hasta 35. ...
In Latin America snapper species have shown great potential for mariculture, including L. guttatus, but it is necessary to study physiological aspects regarding its production. The purpose of this studywas to determine the effects of temperature (24, 29 and 34°C) and salinity (15, 25, 35, 45) on the growth andsurvival of juvenile L. guttatus. All experiments were performed in a recirculation system with daily 300%change of water; in cylindrical 80 L tanks, and three replicates per treatment. 360 specimens were used for the experiments. Experiments were performed with 360 specimens. The results showed that there are differences (P
... An automated shuttlebox was used to conduct the experiments. Variations of the shuttlebox system have been used to determine the preferred temperatures of a number of species (Mortensen et al., 2007;Reynolds & Casterlin, 1977;Schurmann & Steffensen, 1992;Schurmann et al., 1991;Staaks, Kirschbaum & Williot, 1999) as well as to assess turbidity and salinity preferences (Meager & Utne-Palm, 2008;Serrano, Grosell & Serafy, 2010). Shuttleboxes are essentially two-chambered tanks, with a temperature gradient between the chambers. ...
... Stewar-Fielder et al. (2005) y Castillo- Vargasmachuca et al. (2013), y en otras especies de pargos, mientras que en temperaturas menores a 24°C disminuyeron su crecimiento, sin afectar la supervivencia. Serrano et al. (2010) encontraron que el pargo gris L. griseus en condiciones de laboratorio, prefiere salinidades intermedias en el rango de 9-23 y en salinidades extremas reduce su actividad en compensación del mayor gasto energético por osmorregulación. Los resultados de este experimento mostraron que de 86,8 a 90,0% de los juveniles de pargo lunarejo, sin exposición previa a la salinidad, fueron capaces de sobrevivir a una transferencia directa de salinidad 15 hasta 35. ...
In Latin America snapper species have shown great potential for mariculture, including L. guttatus, but it is necessary to study physiological aspects regarding its production. The purpose of this study was to determine the effects of temperature (24, 29 and 34 degrees C) and salinity (15, 25, 35, 45) on the growth and survival of juvenile L. guttatus. All experiments were performed in a recirculation system with daily 300% change of water; in cylindrical 80 L tanks, and three replicates per treatment. 360 specimens were used for the experiments. Experiments were performed with 360 specimens. The results showed that there are differences (P < 0.05) in salinity-temperature interaction. The highest specific growth rate appeared in the treatment of 34 degrees C and salinity of 15. The greatest gain in average body weight was obtained in the treatment of 34 degrees C and salinity of 25. The longer survival was recorded in the treatment of 24 degrees C and salinities of 15 to 35. The low salinity tolerance for this species found shows that L. guttatus has a high potential to grow in lagoon-estuarine systems of low salinity (15) and no more than 35.
... Following this recovery period, individuals were subjected to an 'initial' hypercarbia avoidance challenge. Quantification of hypercarbia agitation and avoidance parameters was performed using a 'shuttle box' choice arena (Loligo Inc., Hobro, Denmark) (Serrano et al. 2010). Kates et al. (2012) provides a description of the 'shuttle box' choice arena, along with a general protocol for the hypercarbia avoidance challenge. ...
Aquatic hypercarbia, either naturally occurring or anthropogenically induced, can have extensive impacts on aquatic environments and resident organisms. While the impact of acute hypercarbia exposure on the behavior and physiology of fishes has been well studied, relatively little work has examined the physiological impact and acclimation capacity of fishes to chronic hypercarbia. To better understand the impacts of prolonged hypercarbia exposure, largemouth bass were held at ambient CO2 (13 mg L(-1)) and elevated CO2 (31 mg L(-1); ≈21,000 µatm) for 58 days. Following this acclimation period, fish were subjected to three separate, yet complementary, experiments: (1) acute hypercarbia challenge of 120 mg L(-1) CO2 for 1 h to quantify physiological and molecular responses; (2) hypercarbia avoidance challenge to compare CO2 agitation and avoidance responses; and (3) swim performance challenge to quantify burst swimming performance. Acclimation to 31 mg L(-1) CO2 resulted in a significant constitutive upregulation of c-fos expression in erythrocytes, combined with significant constitutive expression of hsp70 in both gill and erythrocytes, relative to controls. Largemouth bass acclimated to elevated CO2 also had a reduced glucose response (relative to controls) following an acute CO2 exposure, indicating a reduced stress response to CO2 stressors. In addition, largemouth bass acclimated to elevated CO2 conditions required 50 % higher CO2 concentrations to illicit agitation behaviors and displayed prolonged burst swimming abilities in high CO2 environments relative to controls. Together, results demonstrate that largemouth bass exposed to chronic hypercarbia may possess a physiological advantage during periods of elevated CO2 relative to naïve fish, which may permit increased performance in hypercarbia.
... Clearly, performing laboratory studies as an independent means of validating the apparent water property affinities would be useful. Particularly revealing would be separate temperature, salinity, and DO preference/avoidance trials, whereby fieldcollected juveniles are briefly acclimated to laboratory conditions and their movement is subsequently monitored in relation to water property gradients that have been created in specialized tanks (e.g., Serrano et al. 2010;McManus et al. 2014). Of course, owing to the large size of juvenile goliath grouper, substantially larger behavioral systems than used previously would have to be constructed, which in turn would require storage and manipulation of far greater volumes of water than those used before. ...
While juvenile Atlantic goliath grouper, Epinephelus itajara (Lichtenstein, 1822), are known to depend on mangrove root structure, relationships with water properties (e.g., salinity) and depth remain unclear or understudied. Because availability of suitable mangrove habitat has been suggested as the primary bottleneck to the recovery of this threatened species in the US, we investigated habitat associations of juvenile Atlantic goliath grouper with respect to physical water properties within mangrove habitats. Our study was conducted in six coastal rivers and three canals within the Ten Thousand Islands region of southwest Florida. Results suggested that juvenile Atlantic goliath grouper differed in how they associated with specific mangrove habitats based on season and size. We found that smaller juveniles (<340 mm TL) appeared to have stronger associations to physical water characteristics than larger (≥340 mm TL) juveniles. Both large and small juveniles showed the strongest associations with DO (i.e., >3 mg L−1) within mangrove habitat. For small juveniles, extreme temperatures influenced habitat association; for large juveniles, extreme salinity influenced distribution. We also found evidence that juvenile Atlantic goliath grouper associated more with natural rivers over man-made canals. The present study has utility for delineating suitable mangrove habitats for protection and potentially in the design of sampling surveys that aim to estimate population abundance.
... Other studies have used choice chambers (Benfield and Aldrich 1991, 1992, 1994James et al. 2008;Keiser and Aldrich 1976;Kroon and Housefield 2003) that generally present experimental animals with only two environmental options. Automated selection systems, which continuously adjust salinity levels in choice chambers in response to changes in animal position, are also useful for examining salinity selection in marine organisms (Serrano et al. 2010). ...
Changes in freshwater inflow and salinity patterns
may affect the nursery value of estuarine systems for penaeid
shrimp, but the relationship between salinity and shrimp abundance
is complex and likely confounded by other environmental
variables. Laboratory experiments can provide insights
into salinity selection, and we designed an experimental gradient
tank to examine salinity preferences of juvenile brown
shrimp and white shrimp. Our design uses gently flowing
water to eliminate various physical constraints often associated
with selection experiments. We conducted experiments
with juvenile brown shrimp (12 trials) and white shrimp (seven
trials), to examine selection for salinities along a gradient
from 1 to 42. Data were analyzed using contingency tables
and log-linear modeling to examine relationships with salinity
and possible interactions with temperature. Both brown
shrimp and white shrimp were present in all salinities examined
within the experimental range. In general, brown shrimp
showed a preference for salinities from 17 to 35 and demonstrated
avoidance for the extreme low salinities along the gradient.
Results for white shrimp were not statistically significant,
and this species did not appear to avoid low salinities.
There was no effect of water temperature on the observed
selection patterns for brown or white shrimp. Our results suggest
that although salinity preferences likely exist for these
species, strong distribution trends associated with salinity
gradients in estuaries are likely caused by other environmental
factors.
... Other studies have used choice chambers (Benfield and Aldrich 1991, 1992, 1994; James et al. 2008; Keiser and Aldrich 1976; Kroon and Housefield 2003) that generally present experimental animals with only two environmental options. Automated selection systems, which continuously adjust salinity levels in choice chambers in response to changes in animal position, are also useful for examining salinity selection in marine organisms (Serrano et al. 2010). ...
Changes in freshwater inflow and salinity patterns
may affect the nursery value of estuarine systems for penaeid
shrimp, but the relationship between salinity and shrimp abundance
is complex and likely confounded by other environmental
variables. Laboratory experiments can provide insights
into salinity selection, and we designed an experimental gradient
tank to examine salinity preferences of juvenile brown
shrimp and white shrimp. Our design uses gently flowing
water to eliminate various physical constraints often associated
with selection experiments. We conducted experiments
with juvenile brown shrimp (12 trials) and white shrimp (seven
trials), to examine selection for salinities along a gradient
from 1 to 42. Data were analyzed using contingency tables
and log-linear modeling to examine relationships with salinity
and possible interactions with temperature. Both brown
shrimp and white shrimp were present in all salinities examined
within the experimental range. In general, brown shrimp
showed a preference for salinities from 17 to 35 and demonstrated
avoidance for the extreme low salinities along the gradient.
Results for white shrimp were not statistically significant,
and this species did not appear to avoid low salinities.
There was no effect of water temperature on the observed
selection patterns for brown or white shrimp. Our results suggest
that although salinity preferences likely exist for these
species, strong distribution trends associated with salinity
gradients in estuaries are likely caused by other environmental
factors.
We tracked locations of three fish species in two bays with differing hydrology in SW Florida in 2018–2020 to test the hypotheses about fish residency, movements, and environmental variables. Due to extensive watershed modification, one bay receives less freshwater and the other receives more relative to natural conditions. Home range duration differed for gray snapper (54 ± 6 days), red drum (132 ± 39), and goliath grouper (226 ± 63). Distances between relocation movements were similar for gray snapper and red drum (~ 1.2 km), but farther for goliath grouper (2.3 ± 0.3 km). Relocations were primarily seaward for gray snapper (83%) but varied for the other species. Home range duration related to age for goliath grouper (< 100 days for 1–1.5-year-olds, 300–425 days for 4–4.5-year-olds). Generalized additive models marginally related probability of gray snapper relocating to salinity and temperature whereas relocations of the other species occurred during all environmental conditions. Movement simulations lacking environmental cues produced similar emigration patterns as observed in tagged fish. Overall, results suggest that movements here are not strongly linked to environmental conditions, will be resilient to watershed restoration that should moderate salinity, and have implications for understanding the impacts of localized depletion due to recreational fishing.
Context Movements of purebred and hybrid complexes of species show the interactions that facilitate hybridisation and genetic introgression. Aims This study combines genetic analysis of Acanthopagrus spp. and acoustic tracking to understand the spatial ecology of this species complex. Methods Acanthopagrus australis (yellowfin bream) and the Acanthopagrus hybrid complex of A. australis and Acanthopagrus butcheri (black bream) were tracked using acoustic telemetry within a south-eastern Australian estuary. Key results Movements between A. australis and Acanthopagrus hybrids showed similarities, fish displayed high levels of residency and site fidelity, with peak distributions occurring 15 and 32 km upstream of the river entrance. Offshore movements were recorded for 43% of A. australis and 38% of Acanthopagrus spp. hybrids where fish did not return to the study estuary. Estuarine movement patterns in A. australis and A. spp. hybrids were significantly related to conductivity, freshwater flow, temperature, genetic classification, and capture location. Repetitive spawning migrations were not observed for either A. australis or A. spp. hybrids. Overlap in distributions throughout the spawning period did occur. Conclusions This study highlighted the complexity of estuarine movement patterns in A. australis and Acanthopagrus hybrids because they appear to be dependent on freshwater flow, temperature, and ancestry. Implications A. australis and A. spp. hybrids may be capable of spawning within estuaries, and adult offshore movements may play a role in the genetic mixing of populations.
Larval Atlantic croakers (Micropogonias undulatus) ingress into estuaries from offshore spawning sites during fall and winter. Larvae and early juveniles migrate up‐estuary to oligohaline nurseries where they reside for several months before emigrating seaward. We examined ontogenetic changes in behavioral salinity preference and avoidance as potential contributors to these movement patterns along the estuarine salinity gradient. Four size classes (26‐40, 41‐55, 56‐70, and 71‐85 mm standard length) were acclimated to 10‰ and 18°C, and exposed to horizontal salinity gradients providing five discrete salinity choices: 2, 6, 10, 14, and 18‰. Behavioral salinity preference varied ontogenetically: 26‐40 mm juveniles avoided salinities ≤10‰ and preferred higher salinities, 41‐55 mm juveniles showed a shift toward lower salinities, and 56‐70 mm fish continued this trend by preferring 2‰ and avoiding 18‰. The largest fish tested (71‐85 mm) showed no significant preference or avoidance behavior, although they tended to avoid the low and prefer the high salinities tested. Preference for higher salinities among early (26‐40 mm) juveniles may facilitate orientation in higher‐salinity bottom waters, assisting up‐estuary immigration to oligohaline nurseries via residual bottom layer inflow. Low salinity preference by 56‐70 mm juveniles is consistent with their residence in oligohaline areas. We also conducted feeding and growth experiments, at 18°C, on 30‐40 mm and 75‐85 mm fish, corresponding to the smallest and largest fish in the salinity preference trials. Smaller juveniles showed no significant energetic advantage in oligohaline versus mesohaline conditions. However, larger juveniles grew significantly faster at 18‰ than 2‰, indicating that movement down‐estuary during summer and fall improves growth capacity later in the nursery season. Increased precipitation and river discharge predicted from climate change, and associated stronger net up‐estuary flow of saline bottom waters, may facilitate up‐estuary immigration of early juvenile Atlantic croakers through their attraction to higher salinity demonstrated by the present work.
Los estudios de evasión espacial en sistemas multicompartimentado han demostrado la habilidad de algunos organismos para detectar la contaminación y huir hacia zonas menos contaminadas. Esta respuesta previene efectos adversos a nivel individual, aunque lleva a una pérdida local de especies, lo que podría provocar problemas a nivel ecosistémico. La evasión es estudiada mediante sistemas de ensayos con una exposición que simula un gradiente de contaminación y permite que los organismos elijan las zonas más favorables. Debido a que hay pocos estudios en comparación con las respuestas ecotoxicológicas tradicionales, es crucial saber cuán sensible es la respuesta de evasión frente a las demás respuestas ampliamente usadas. El presente trabajo se centró en comparar la sensibilidad de la evasión espacial con las respuestas ecotoxicológicas tradicionales mediante tres herramientas: representación del perfil de sensibilidad por grupos biológicos, creación de la distribución de las especies en función de la sensibilidad y finalmente calculándose la concentración de riesgo a 5% de las especies. El estudio ofrece una visión de la sensibilidad de la respuesta de evasión para especies de agua dulce y marinas como una señal del potencial riesgo asociado a la contaminación y discute la relevancia ecológica de dicha respuesta. Se ha observado que la evasión es una respuesta muy sensible al ser comparada con otras respuestas ecotoxicológicas y se constata la importancia de incluir dicha respuesta para evaluar los riesgos ecológicos de los contaminantes sobre la dispersión de los organismos. Palabras clave: evasión espacial; sistema multicompartimentado; exposición no forzada; cobre; HC5, SSD.
This study aimed to reveal salinity preference of juveniles of an amphidromous goby, Sumi‐ukigori Gymnogobius petschiliensis, while migrating to a freshwater area. Salinity choice experiments revealed that juveniles of this species significantly prefer brackish water (salinity 20) to freshwater (salinity 0) when acclimated to a salinity of 20 in advance. Additional experiments revealed no preference between brackish water and seawater (salinity 35). Since body size was not correlated with the strength of preference for brackish water, and adults of this species are also known to prefer brackish water at a salinity of 20 to freshwater, the preference for saline water may be consistent after migration to a freshwater area. Considering that juvenile G. petschiliensis would often migrate to freshwater areas just after entering streams, the migration should be against its salinity preference. This directly contrasts with other diadromous species, which prefer the salinity of destination areas during and after migration. Adult and juvenile G. petschiliensis may take advantage of high euryhalinity to choose habitats where such ecological costs, such as high predation risk and interspecific competition, are low (i.e. freshwater areas).
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This study investigated the relationships between behavioural responses of Atlantic salmon Salmo salar smolts to saltwater (SW) exposure and physiological characteristics of smolts in laboratory experiments. It concurrently described the behaviour of acoustically tagged smolts with respect to SW and tidal cycles during estuary migration. Salmo salar smolts increased their use of SW relative to fresh water (FW) from April to June in laboratory experiments. Mean preference for SW never exceeded 50% of time in any group. Preference for SW increased throughout the course of smolt development. Maximum continuous time spent in SW was positively related to gill Na(+) , K(+) -ATPase (NKA) activity and osmoregulatory performance in full-strength SW (measured as change in gill NKA activity and plasma osmolality). Smolts decreased depth upon reaching areas of the Penobscot Estuary where SW was present, and all fish became more surface oriented during passage from head of tide to the ocean. Acoustically tagged, migrating smolts with low gill NKA activity moved faster in FW reaches of the estuary than those with higher gill NKA activity. There was no difference in movement rate through SW reaches of the estuary based on gill NKA activity. Migrating fish moved with tidal flow during the passage of the lower estuary based on the observed patterns in both vertical and horizontal movements. The results indicate that smolts select low-salinity water during estuary migration and use tidal currents to minimize energetic investment in seaward migration. Seasonal changes in osmoregulatory ability highlight the importance of the timing of stocking and estuary arrival.
Bigheaded carps are non-native invasive fishes that have quickly become the most abundant fishes in many portions of the Midwestern United States. While the spread of bigheaded carps into the Great Lakes is currently impeded by three electrified barriers, these fish have the potential to negatively impact the Great Lakes ecosystem if this barrier is breached, and these barriers may be particularly vulnerable to the passage of small fishes. As such, novel barrier technologies would provide an additional mechanism to prevent bigheaded carps from invading the Great Lakes, and provide much needed redundancy to the current electric barrier. The current study used a combination of molecular and behavioral experiments to determine the effectiveness of carbon dioxide as a chemical deterrent for larval and juvenile fishes, with an emphasis on bigheaded carps. Juvenile silver carp (Hypophthalmichthys molitrix), bighead carp (H. nobilis), bluegill (Lepomis macrochirus) and largemouth bass (Micropterus salmoides) showed avoidance of elevated CO2 environments at approximately 200 mg/L. Additionally, exposure to 120 mg/L CO2 resulted in the induction of hsp70 mRNA in 8 days old silver carp fry, while gill c-fos transcripts increased following hypercarbia exposure in all juvenile species examined. Together, our results show that CO2 has potential to deter the movement of larval and juvenile fishes.
Many estuarine species are euryhaline, tolerating a broad range of salinity conditions, such that data on their salinity tolerances can provide little information about a species' distribution and abundance. This is particularly true for nonnative species, known to be tolerant of a broad range of conditions. Instead, data on a species' abiotic or habitat preferences may improve prediction of a nonnative species' potential range, if introduced or if undergoing range expansion. At minimum, information about abiotic preferences may be telling of areas where the probability of nonnative occurrence or density may be higher, and if present, of areas that confer higher fitness. In this study, the salinity preference of the nonnative African jewelfish (Hemichromis letourneuxi), a recent and rapidly-expanding invader in the Florida Everglades, was quantified in laboratory trials. Despite the broad salinity tolerance of African jewelfish (up to 50), trials show a strong preference for freshwater conditions. When presented with a salinity gradient, over 50% of observations in timed videotaped trials were collected in the lowest salinity chamber (0.3), suggesting an affinity for low salinity, which was unaffected by the sex or body condition of study fish. Fish clearly avoided mid and full salinity conditions. Findings suggest that their distribution may be considerably more limited, and that the species may have higher invasion success in oligohaline habitats, than predicted based on their salinity tolerance. Results have important implications for nonnative species niche modeling, and argue for better integration of behavior along with physiological responses when examining species distributions in dynamic environments.
Upon arrival in a novel environment, invasive species have the potential to cause negative consequences at their new location. Rather than try to eliminate invasive species after introduction, preventing their spread is a more efficient strategy to mitigate impact. The current study used a laboratory setting to quantify the efficacy of elevated carbon dioxide (CO2) in water to act as a nonphysical barrier to deter fish movement. Our focus was on deterring the movements of silver carp (Hypophthalmichthys molitrix) and bighead carp (Hypophthalmichthys nobilis), but largemouth bass (Micropterus salmoides) and bluegill (Lepomis macrochirus) were also examined to quantify the impact of elevated CO2 on native species. Exposure of all species to 30 mg.L-1 dissolved CO2 for 1 h, compared with ambient CO2 concentrations of 10 mg.L-1, resulted in an elevated stress response, along with alterations to ionic-osmotic balance. Exposure of fish to 70 mg.L-1 CO2 caused a reduction in ventilation rates after 1 h, while both silver carp and bighead carp lost equilibrium. Silver carp, largemouth bass, and bluegill also showed avoidance of CO2 at approximately 100 mg.L-1. Together, results suggest that zones of elevated CO2 have potential to deter the movement of fishes.
Newly recruited juvenile gray snapper Lutjanus griseus were collected each fall for two consecutive years (2000 and 2001) from sites in Florida and North Carolina. Spawning, settlement, and growth patterns were compared across sites based on otolith microstructure. Larval otolith growth trajectories were generally similar for larvae from different sites and years; however, the mean pelagic larval duration (PLD) was 1 d longer for fish from North Carolina than for fish from the more southern sites. As a result, fish were larger at settlement to North Carolina. Estimated juvenile growth rates ranged between 0.62 and 0.88 mm/d and differed across sites and years, growth being generally faster at the southern sites. Water temperature accounts for some of this variability; however, site-specific differences in other factors probably contributed to some of the observed differences in growth. Back-calculated spawning patterns showed a lunar association with the new and first-quarter moons at all sites except for North Carolina. Settlement patterns were lunar cyclic as well: settlement pulsed during the third-quarter and new moons at all sites, and in North Carolina an additional pulse associated with the full moon was present. Patterns of larval and juvenile growth coupled with recruitment dynamics across the latitudinal gradient are consistent with northward Gulf Stream transport of larvae from southern spawning sites.
A 14 mo trawl survey was conducted at 8 study sites in Biscayne Bay, Florida, USA, to compare the species composition and structure of juvenile fish assemblages found near the mouths of freshwater flood control canals with those in similar areas with relatively stable salinity regimes. Water temperature, salinity, dissolved oxygen and depth measurements were recorded during fish sampling and bottom vegetation was also quantified. The survey yielded a total of 38134 individuals from 95 taxa. Fish species composition was similar among sites, but more species were collected from stable-versus variable-salinity areas. Mean fish abundance and the mean abundances of Eucinostomus gula, Lagodon rhomboides, Opsanus beta and Lutjanus griseus shared a general pattern of increase from north to south, with highest values occurring at one or more of the canal-influenced sites. In contrast, mean species richness and the mean abundances of Lucania parva, Haemulon sciurus, H. plumieri, and H. parra were significantly greater at stable-salinity sites than at variable-salinity sites. Freshwater challenge experiments were then conducted on each of the fishes above, as well as on 2 relatively uncommon species, Cynoscion nebulosus and Cyprinodon variegatus. The mortality of groups exposed to a single, rapid, freshwater pulse (i.e. salinity was changed from approximately 32 ppt to 0 to 32 ppt over 2 h) was compared with that of controls. Of the 8 fishes that dominated the nearshore habitats of Biscayne Bay, 5 exhibited no mortality and L. rhomboides, L. parva, and H. plumieri exhibited 12.5, 50 and 100% mortality rates, respectively. Mortality was 100% for the relatively uncommon C. nebulosus and C. variegatus. Results suggest that the differential osmoregulatory abilities of the species tested may underlie some, but not all, of the structural differences observed between fish assemblages from stable-salinity habitats versus those adjacent to freshwater canals.
Many fishes are thought to make diel, seasonal and/or ontogenetic migrations among seagrass, mangrove, and coral reef habitats. However, most evidence of such movement has been inferred from density and size structure differences among these habitats in tropical waters. The aim of the present study was to directly evaluate multiple habitat use by an ecologically and economically important reef fish, the gray snapper Lutjanus griseus, in subtropical waters. An integrated set of activities was conducted, including tagging and tracking of individuals and underwater video photography to examine the spatial and temporal dynamics of movements among neighboring mangrove, seagrass, and coral reef habitats in the northern Florida Keys, USA. Results of ultrasonic acoustic and mini-archival tagging indicated that L. griseus exhibits: (1) a distinct diel migration pattern, whereby shallow seagrass beds are frequented nocturnally and mangroves and other habitats with complex structure are occupied diurnally, and (2) bay-to-ocean movement, occurring during the known spawning season of L. griseus in this region. Video photography confirmed diel movement among seagrass and mangrove habitats. Results of this subtropical study corroborate direct and indirect evidence obtained in tropical waters of multiple inshore habitat use by L. griseus, as well as its seasonal movement into or towards offshore reefs. For resource managers charged with designing and implementing management plans for subtropical coastal habitats and fisheries, our findings provide direct support for the strategy of conserving both inshore seagrass and mangrove habitats as well as offshore coral reefs. tagging, Underwater video
Eels colonize either marine, estuarine or freshwater habitats, with marine and estuarine eels tending to grow faster than freshwater eels. The reasons for these divergent migratory tactics and growth trajectories remain poorly -understood. In order to investigate the role of salinity preferences of glass eels in the control of habitat selection and growth plasticity, we sorted different contingents of glass eels Anguilla anguilla through 2 consecutive salinity preference tests. This allowed us to study the link between salinity preference and locomotor activity (i.e. positive rheotaxis), and to distinguish contingents of glass eels that were either plastic or fixed in their preference for freshwater (FW) or saltwater (SW). Subsequently, we monitored somatic growth of the different contingents in controlled SW and FW rearing conditions. Preference for FW was linked to high locomotor activity, a behavioral pattern likely to promote colonization of FW habitats in the wild. Accordingly, FWC (FW contingent, i.e. glass eels that preferred FW twice) exhibited poor growth, similar to those observed in wild FW eel populations. In contrast, preference for SW was linked to low locomotor activity, and the SWC (SW contingent, i.e. glass eels that preferred SW twice) had high growth rates in SW, as observed in wild marine and estuarine populations. The PCC (plastic contingent, i.e. glass eels that swappped their salinity preference) had an intermediary growth status that could be related to the 'nomad' life style of eels migrating between different habitat types during their life. Growth was significantly higher in SW compared to FW in all contingents, indicating that habitat salinity may directly affect growth, irrespective of food availability. Our results demonstrated that glass eel salinity preference was linked to their locomotor activity and growth performance, and provided a comprehensive ecological mechanism for the control of habitat distribution and growth patterns observed in wild eel populations.
Seasonal changes in freshwater inflow and other environmental conditions may induce changes in density and species composition of mangrove fishes along estuarine gradients. Fishes within mangrove habitats in a subtropical estuary were sampled monthly from May 1989 to May 1990, using block nets with rotenone and visual censuses. At 18 stations, temperature ranged from 22 to 34°C, depth from 10 to 104cm and underwater visibility from 1 to 13m. Salinity ranged from 0 to 60 upstream, and 35 to 54 mid- and downstream. A total of 573191 individuals (76 species) was observed or collected, with an average density of 6·5 fish m−2. Engraulidae, Atherinidae, Poeciliidae and Cyprinodontidae numerically dominated the assemblage. Distinct assemblages occurred up-, mid- and downstream and maintained coherent groups in these gradient positions over the seasons. Residents totalled 94·5% of the individuals, estuarine transients comprised 5·1% and occasional marine visitors were less than 0·4%. Densities of resident fishes peaked in winter as temperatures and water levels fell, uncorrelated with changes in salinity. These observations suggest that mangrove habitats may sustain diverse and abundant fish communities dominated by euryhaline residents. Although estuarine transients were consistently rare in upstream sub-basins, downstream were found numerous sub-adults of species occurring as adults on nearby reefs (Lutjanidae, Haemulidae). Thus, reef-associated estuarine transients may be abundant in mangrove habitats having near-marine salinities. Contrary to expectations, mangrove habitats in northeastern Florida bay did not function as a nursery as defined under the nursery-ground paradigm: young-of-the-year juveniles of estuarine transient species did not seek low salinity sub-basins. However, northeastern Florida Bay may not be representative of most mangrove estuaries as the area: (1) is without lunar tides and related circulation; (2) has low and variable amounts of submersed vegetation; and (3) experiences severe hypersaline conditions.
We investigated salinity and temperature effects on routine metabolic rate (RMR), tempera- ture tolerance (CTMax, critical thermal maximum), and salinity toleranc eo fLimia melanonotata, a poeciliid fish that occurs in west-central inland waters of Hispaniola. Routine metabolic rate and CTMax were mea- sured in fish acclimated to three salinities (0, 30, and 60 ppt) and temperatures (25°, 30°, and 35°C) for nine temperature-salinity combinations. Salinity and temperature did not significantly interact in their effect on RMR. For combined salinity acclimations, adjusted RMR (ANCOVA) was significantly lower at 25°C than either 30° or 35°C. For combined temperature acclimations, mean RMR was significantly lower at 60 ppt than either 0 or 30 ppt. Salinity and temperature had a significant interactive effect on temperature tolerance. Mean CTMax was significantly higher at 30° than 25°C at all salinities, but at 35°C was significantly higher than at 25° or 30°C only among fish acclimated in fresh water. Fish exposed to a chronic increase in salinity experienced most mortality in a salinity range of 70-107 ppt, with females exhibiting greater salinity tolerance than males. Limia melanonotata approaches the upper extreme in salinity and temperature tolerances known for poeciliids. Our results also suggest that L. melanonotata may reduce energy expenditures at environ- mental extremes to tolerate harsh conditions for extended periods. Despite its eurythermal and euryhaline adaptations, L. melanonotata has a relatively restricted inland range in Hispaniola and is unknown from inshore brackish or marine habitats. The present distribution of this species and congeners may be the result of a combination of factors that include historical zoogeography and ecological requirements.
We examined the role of salinity, body size, and energetic state in determining low temperature tolerance of young-of-the-year (YOY) striped bass (Morone saxatilis) and used this information to map optimal overwintering habitat in the Hudson River estuary. A long-term experiment compared survival at 15 ppt and 30 ppt. In additional experiments, winter-acclimated fish were exposed to temperature declines (2.3°C·day1 to 1°C·week1) at salinities from 0 ppt to 35 ppt. Highest survival at low temperatures was consistently observed at intermediate salinities. These results suggest that the observed distribution of overwintering striped bass is related to physiological constraints on osmo regulatory ability at low temperatures. Low temperature tolerance appeared unrelated to body size and energetic state. Salinity profiles were used to describe the location and extent of optimal wintering habitats under various hydrographic regimes. The location of optimal habitats was displaced by over 27 km along the river axis because of variation in salinity regime. Changes in the availability of optimal habitat may be responsible for variation in recruitment to the Hudson River population. These results demonstrate the need to consider a holistic approach encompassing all seasons of the year in assessing habitat requirements of fishes.
By determining the microclimates that an animal experiences, habitats influence an animal's physiological capacities and ultimately its demographic and ecological performance. As a result, the ecology of organisms-especially of ectotherms-can be profoundly affected by the physiological consequences of habitat selection. Early ecologists such as Shelford and Chapman appreciated these issues, but most later ones tended to ignore physiology and instead focused on biotic interactions (e.g., competition). Recent technical and conceptual developments are now fostering a reintroduction of physiology into ecology. For issues relevant to thermal physiology, three steps are involved. First, the microclimates available in a habitat must be mapped. For ectotherms, this involves determining the operative environmental temperatures (Te)-that is, the potential body temperatures available in a habitat. Biophysical techniques can now generate Te maps with considerable accuracy. Second, the physiological effects of body temperature must be quantified. This requires laboratory studies of the effect of temperature on key performance traits. Third, the physiological suitability of habitats can be predicted by integrating the above environmental and physiological data. Analyses of the physiological consequences of habitat selection are exemplified in several case studies, and the importance of considering food and other factors in the analyses is stressed. An extension to endotherms is briefly discussed.
The behavioral thermoregulation of rainbow trout Oncorhynchus mykiss was investigated in a shuttlebox at normoxia and at three levels of hypoxia: 13.3, 9.3 and 5.3 kPa. The final preferred temperatures at normoxia, and at 13.3, 9.3 and 5.3 kPa, were 16.1, 14.9, 15.0 and 12.7-degrees-C, respectively. A decreased rate of metabolism and an increased blood oxygen-affinity are among the physiological advantages of selecting a lower temperature during hypoxia. It is suggested that catecholamines may play a part in controlling temperature selection during hypoxia. In natural environments, this behaviour may result in habitat shifts of fish living in heterothermal environments with changing oxygen tensions.
Fringing mangrove forests and seagrass beds harbor high densities of juvenile snappers and grunts compared to bare substrates, but their occupancy of these habitats is not homogeneous at ecologically meaningful scales, thus limiting our ability to compare habitat value. Here, density and size information were used to determine how gray snapper, Lutjanus griseus (Linnaeus, 1758) and bluestriped grunt, Haemulon sciurus (Shaw, 1803), use vegetated habitats during their ontogeny, and how their use of mangrove forests varied with season across broad spatial scales and physicochemical conditions. Both species exhibited a three-stage ontogenetic strategy: (1) settlement and grow-out (8-10 mo) within seagrass beds, (2) expansion to mangrove habitats at 10-12 cm total length, and (3) increasing utilization of inland mangroves during the dry season and with increasing body size. For fishes inhabiting mangroves, multivariate tests revealed that the factors distance from oceanic inlet and water depth were stronger predictors of reef fish utilization than the factors latitude, temperature, or habitat width. These findings highlight that the nursery function of mangrove shorelines is likely limited to the area of immediately accessible habitat, and that more expansive forests may contain a substantial number of larger adult individuals.
From 1998 to 2005, 537 visual fish surveys were conducted along a 50-km stretch of mangrove-lined shoreline in the vicinity of Biscayne Bay (southeastern Florida, USA). The shoreline lies directly downstream of a major wetlands restoration project that aims to return more natural salinity regimes to the western margin of the region's coastal bays. As part of a "baseline" ecological assessment, we applied the delta approach to examine spatial and temporal patterns of mangrove habitat use by three fishes: Lutjanus griseus (Linnaeus, 1758), Sphyraena barracuda (Walbaum, 1792), and Floridichthys carpio (gunther, 1866). Along a north-south gradient, seasonal variation in their size-composition and three abundance metrics (occurrence, concentration, and density) was quantified and overall correlations with water salinity, depth, and temperature were evaluated using multiple regression. Results indicated that the shoreline is used by subadult and adult L. griseus and by mostly juvenile S. barracuda; for both species, highest abundance metric values occurred during the wet season, generally increasing southwards. In contrast, F. carpio were almost exclusively of adult (mature) sizes, with greatest values during the dry season at the shoreline's northern extent. For all species, water depth and/or temperature had a significant effect on abundance metrics. positive correlations were found for L. griseus and S. barracuda abundance metrics, whereas the reverse was true for F. carpio. To date, most mangrove-fish studies have evaluated a single measure of fish abundance, usually density. We suggest consideration of occurrence and concentration, in addition to density, has value in an assessment and monitoring context as well as for gaining insight into how a given fish species disperses and clusters within habitats and across gradients.
Biscayne Bay is a shallow subtropical lagoon on Florida's southeastern coast that is bordered to the west by the mainland and to the east by barrier islands and keys. Fish assemblages inhabiting two types of mangrove-lined shoreline that encompass the Bay were examined using a visual 'belt-transect' census method over four consecutive seasons. Several significant differences were evident between shoreline habitats in terms of fish species composition, taxonomic richness and taxon-specific densities; seasonal changes and fish size-structure differences were few. The mangrove shorelines along the mainland (ML) consistently harbored less fish taxa than those on the leeward side of the islands and keys (LK), but harbored higher densities of several euryhaline forms (i.e., killifishes and livebearers). Densities of fishes that are typically associated with coral reef habitats (i.e., snappers and grunts) tended to be higher within LK vs ML mangrove shorelines, but there were exceptions (e.g., great barracuda, Sphyraena barracuda). For five fish species, length-frequency distributions were compared between the Bay's mangrove shorelines and nearby coral reef habitats. These data comparisons lent partial support to an ontogenetic 'mangrove-to-reef' migration model for only two of the five species examined. Results suggest that these shoreline habitats play varying ontogenetic and trophic roles, depending on location, season and fish species. Biscayne Bay's mangrove shoreline fish assemblages appear to reflect: (1) proximity of the mangroves that they occupy to offshore reef habitats; (2) salinity regime along the shoreline; and (3) water depths within the mangrove forest interior. The fish assemblage information collected here may serve as a 'baseline' in future assessments of fishing impacts or the effects of other anthropogenic changes to Biscayne Bay and its watershed.
Intermoult Carcinus maenas (Crustacea: Decapoda) exhibit a range of carapace colours from green through orange to red, reflecting increasing lengths of intermoult duration, with red crabs less tolerant than green crabs of low salinity. The salinity preference behaviour of red and green colour forms was investigated. Red crabs vacated low salinities earlier than green crabs and green crabs had a lower tolerance range. Acclimation to either low or high salinities affected red and green crabs in a similar manner; the lower the acclimation salinity the earlier the time of exit from the low salinity and vice versa; the higher the acclimation salinity, the longer the crabs remained in the low salinity. Carcinus of both colour forms were shown to be able to discriminate between salinities separated by a difference as little as 0.5‰.
The ecosystems of South Florida are unique in the world. The defining features of the natural Everglades (large spatial scale, temporal patterns of water storage and sheetflow, and low nutrient levels) historically allowed a mosaic of habitats with characteristic animals. Massive hydrological alterations have halved the Everglades, and ecological sustainability requires fundamental changes in management.
The US Man and the Biosphere Human-Dominated Systems Directorate is conducting a case study of South Florida using ecosystem management as a framework for exploring options for mutually dependent sustainability of society and the environment. A new methodology was developed to specify sustainability goals, characterize human factors affecting the ecosystem, and conduct scenario/consequence analyses to examine ecological and societal implications. South Florida has sufficient water for urban, agricultural, and ecological needs, but most water drains to the sea through the system of canals; thus, the issue is not competition for resources but storage and management of water. The goal is to reestablish the natural system for water quantity, timing, and distribution over a sufficient area to restore the essence of the Everglades.
The societal sustainability in the Everglades Agricultural Area (EAA) is at risk because of soil degradation, vulnerability of sugar price supports, policies affecting Cuban sugar imports, and political/economic forces aligned against sugar production. One scenario suggested using the EAA for water storage while under private sugar production, thereby linking sustainability of the ecological system with societal sustainability. Further analyses are needed, but the US MAB project suggests achieving ecological sustainability consistent with societal sustainability may be feasible.
Purple shore crabs, Hemigrapsus nudus (Crustacea: Decapoda), can survive indefinitely in salinities of 8 (25% SW), but also tolerate short-term exposure to salinities as low as 2. In the laboratory their salinity preference range, determined from choice chamber experiments, is 22–32 and they can discriminate between pairs of salinities separated by a difference of 2. These crabs show a strong positive thigmotaxis and a weak negative phototaxis and tend to choose environments with available shelter. The presence of shelter significantly alters the behaviour of this species. When shelter is available the salinity preference range is 10–32. Even in salinities below this preference range, the presence of shelter prolongs the time spent in the lower test salinities. This change in behaviour has implications on the crab's physiology: the haemolymph osmolality falls to lower levels when crabs remain in low salinity under shelters. In the field, H. nudus is found in creeks with salinities close to freshwater and they may remain in this salinity for up to 11 h, if there are rocks under which to shelter. An increase in habitat complexity increases the number of crabs that are found within the creek. These crabs in the low salinity environment have a lower haemolymph osmolality than crabs on the nearby open shore. In H. nudus the behavioural selection of a shelter appears to outweigh the physiological costs associated with osmotic regulation of the body fluids. Therefore, the distribution of H. nudus in estuaries may depend more on the availability of suitable habitats rather than the salinity tolerance of this species.
Gray snapper, Lutjanus griseus, were sampled from recreational headboat and commercial landings along the east coast of Florida, 1994-97. Fish were weighed (g) and measured (total length, TL, in mm), and sagittal otoliths were removed for aging. Marginal increment analysis on sectioned otoliths (n=1243) confirmed annulus formation in June and July. The oldest fish examined was 24 years old and measured 760 mm TL. Weight-length relations were not significantly different by sex. Weight-length relations were significantly different (F=39.198, P<0.001, df=10,705) for fish measured from the headboat survey from 1982-97 between north Florida (W=8.4 × 10-9 × TL3.08, n=4034) and south Florida (W=5.45 × 10-9 × TL3.15, n=6670), where W = total weight (kg). The TL-otolith radius (OR) relationships were described by the following equations: TL = (10.02 × OR) - 52.98 (r2=0.90, n=519, north Florida), and TL = (9.90 × OR) - 91.68 (r2=0.78, n=724, south Florida). Mean lengths at age from back-calculations to the last annulus ranged from 121 mm at the end of age 1 to 740 mm at age 24 for north Florida, and 227 mm at age 2 to 495 mm at age 15 for south Florida. The von Bertalanffy growth equations were Lt = 717 × (1-e(-0.17 (t + 0.025))) for north Florida and Lt=625 × (1 - e(-0.13 (t + 1.33))) for south Florida. Estimates of M ranged from 0.14 to 0.43 for north Florida and from 0.29 to 0.38 for south Florida. Estimates of Z averaged 0.34 for north Florida and 0.95 for south Florida. Recruitment to the fisheries occurred between ages 5 and 8 for north Florida and ages 4 and 5 for south Florida. Estimates of F for gray snapper by area were 0.16 for north Florida and 0.66 for south Florida.
The euryhaline milkfish (Chanos chanos) is an excellent subject for studies of the physiological and behavioral processes involved in salinity adaptation. In this study, energy partitioning for metabolism, activity and growth, maximal activity performance and blood osmotic concentrations were assessed at two activity levels in juvenile milkfish fed equal rations and maintained at a relatively constant temperature (262 C) and at salinities (15, 35 and 55 ?) that represented a wide range of osmoregulatory challenges. Changes in the measured parameters were not consistently related to the magnitude of the trans-integumentary osmotic gradients. Routine oxygen consumption rates were high in 35 ? salinity (mean 1 s.e.m. 1678 mg O2 kg-1 h-1) and comparably low in 15 and 55 ? salinity (1336 and 1273 mg O2 kg-1 h-1, respectively). Routine activity levels (relative swimming velocity) were highest in 35 ? salinity (0. 960.04 L s-1), where L is standard length, intermediate in 15 ? salinity (0.770.03 L s-1) and lowest in 55 ? salinity (0.670.03 L s-1). Growth was significantly higher in 55 ? salinity (3.40.2 % increase in wet body mass per day) than in 35 ? salinity (2.40.2 % increase per day) and intermediate in 15 ? salinity (2.90.5 % increase per day). Maximum swimming velocities decreased with increases in salinity, from 9.90.7 L s-1 in 15 ? salinity to 6.60. 5 L s-1 in 55 ? salinity. Sustained swimming activity above routine levels for 2 h resulted in an increase in blood osmotic concentrations in milkfish in 55 ? salinity, but osmoregulation was re-established during the second 2 h of activity. Thus, patterns of variation in metabolic rate and growth were largely parallel to variations in routine activity although, comparing 15 and 55 ? salinity, elevated maintenance costs for osmoregulation at the high salinity were detectable. Reduced osmoregulatory abilities and reductions in maximal swimming performance suggest that high salinity may constrain activity. The results demonstrate that investigations of salinity adaptation in euryhaline fishes should take into account the interactive effects of salinity on physiology and behavior.
Documented interest in the fishery resources of Florida Bay dates from the earliest accounts of human activity. However, prior to the 1940's, fishing activities were largely subsistence oriented, providing only supplemental family income. The first large-scale directed fishery was for striped mullet. Increased development of south Florida, improved transportation, and population growth all led to increased sport fishing activities during the 1940's and 1950's. By the early 1970's, there were an estimated 25 000 recreational fishing trips a year to Florida Bay. Commercial activities reached a peak between 1977 and 1978 when over 350 individuals held permits to guide or fish commercially using nets, hook-and-line, or traps. Concern for the conservation of Florida Bay's marine resources quickly followed the explosion of commercial and recreational use occurring in the late 1940's. Florida Bay was added to Everglades National Park in 1950 and, in 1951, the first special government regulations were established to control the methods, species, and locations of fish harvest, although no systematic effort was made to collect accurate catch and harvest statistics until 1958. The National Park Service (NPS) monitoring program has provided detailed data on the fishing effort and harvest of both commercial and recreational fisheries up to the present time. The total recreational fish harvest from Florida Bay by guided and non-guided parties has ranged between 700 000 and 800 000 fish per year since 1984. Species most frequently sought by guide fishermen include tarpon, bonefish, snook, spotted seatrout, gray snapper, red drum, and Spanish mackerel. -from Author
The study of animal function is organized more or less under three heads, which in everyday language are, as applied to a machine, what it can do, how it works, and what makes it go. Insofar as fields of study can be classified in biology these divisions of the subject are ordinarily considered to be autecology, physiology, and biochemistry, with a great deal of individual taste governing the label any particular worker may choose for himself. The chapter discusses what fish can do in relation to their environment and therefore largely autecology. The chapter focuses on the action of the environment on metabolism and the effects of this action on the activity of the organism.
Physiological response of tropical organisms to salinity changes was studied for some marine, estuarine and freshwater fishes (Astyanax bimaculatus, Petenia karussii, Cyprinodon dearborni, and Oreochromis mossambicus), marine and freshwater crustaceans (Penaeus brasiliensis, Penaeus schmitti and Macrobrachium carcinus), and marine bivalves (Perna perna, Crassostrea rhizophorae, and Arca zebra) collected from Northeast Venezuela. They were acclimated for four weeks at various salinities, and (1) placed at high salinities to determine mean lethal salinity, (2) tested by increasing salinity 5 ‰ per day to define upper lethal salinity tolerance limit, or (3) observed in a saline gradient tank to determine salinity preference. Acclimation level was the most significant factor. This phenomenon is important for tropical aquatic organisms in shallow waters, where they can adapt to high salinity during the dry season and cannot lose their acclimation level at low salinity during abrupt rain. For saline adaptation of tropical organisms, this behavior will contribute to their proliferation and distribution in fluctuating salinity environments.
Marshland drainage and water regulation have greatly altered the Florida Everglades. One of the most visible ecological impacts has been a drastic decline in nesting populations of wading birds, and several specific hypotheses have been advanced to explain the decline. Recent efforts at ecological restoration have concentrated on reestablishing more natural seasonal hydropatterns in freshwater marsh areas now used extensively by the wading birds. However, nesting colonies were originally concentrated along the estuarine mangrove edge of the system rather than around upstream marshes. Hydrological simulation models have been used to reconstruct what hydrological conditions might have been like in the natural system, and these simulations indicate that freshwater pools near and flows to the estuary have been drastically reduced, especially late in the annual spring drying season. An experimental program of increased water releases to the estuary could be used to test whether estuarine restoration is a necessary condition for recovery of wading bird populations. This program would require a substantial commitment to deliver runoff from the Everglades Agricultural Area into the marshes, and to minimize water diversions for flood control and well field recharge
Preference chambers are widely used to measure the responses of aquatic organisms to different environmental gradients, such as temperature, salinity, and pollutants. Most of the preference chambers used to date have been handicapped by the presence of one or more confounding variables, including differential light intensities and water depths and the presence of cover. We present a design and test results for an annular preference chamber with uniform environment water depth, light intensity, and cover. Preliminary testing with juvenile anadromous rainbow trout Oncorhynchus mykiss showed that they selected temperatures (±SE) of 18.1 ± 0.3°C, a result that compares favorably with values reported in the literature. We demonstrate that the annular chamber is a viable alternative to the more traditional horizontal, vertical, or shuttlebox-type designs for preference studies of aquatic organisms.
The objective of this research was to determine the effect of freshwater acclimation on the swimming performance and plasma osmolarity of gulf killifish Fundulus grandis. Fish were acclimated to either freshwater or brackish water (10‰ salinity) for 10 d before experimentation. Plasma osmolarity was significantly lower in the freshwater-acclimated fish; however, no significant changes occurred in plasma osmolarity in fish recovering from a swim challenge at either salinity. Critical swimming speeds of the fish acclimated to freshwater were significantly lower than those of fish acclimated to brackish water. Furthermore, the swimming challenge caused 40% mortality in the freshwater fish but no mortality in the brackish-water fish. Acclimation of gulf killifish to freshwater environments appears to have a substantial metabolic cost.
In choice experiments Carcinus was found to have a preferred salinity range which lies between 80% S.W.‐120% S.W. (with ambient salinity at 34‰). Salinities separated by intervals of 10% S.W. were not distinguished, but differences of 25% S.W. were clearly distinguished in choices up to and including 50% S.W. v 75% S.W. and above 125% S.W., given the choice of 125% S.W. v 150% S.W. The results are discussed in the context of earlier work in which salinity cycles have been demonstrated to entrain locomotor tidal rhythmicity in Carcinus. Increases or decreases of salinity from ambient seawater exogenously induce increased locomotor activity, here defined as halokinesis.