Article

Nocturnal fish utilization of a subtropical mangrove‐seagrass ecotone

June 2010
Marine Ecology 31(2):364 - 374

DOI:10.1111/j.1439-0485.2009.00337.x

Authors:

Shark Research Foundation

Whereas diel fish migration between mangrove and seagrass habitats has been recognized for decades, quantitative studies have focused mainly on diurnal patterns of fish distribution and abundance. In general, previous studies have shown that fish abundances decline with increasing distance from mangroves; however, evidence for such a pattern at night, when many fishes are actively feeding, is scarce. The present study is the first to report nocturnal fish abundances along a continuous distance gradient from mangroves across adjacent seagrass habitat (0–120 m). Here, we used nocturnal seine sampling to test the null hypothesis (based on diurnal studies and limited nocturnal work) that fish abundance would decrease with increasing distance from shoreline. We focused on species and life-stage-specific abundance patterns of Lutjanus griseus, Sphyraena barracuda, Archosargus rhomboidalis, and Haemulon sciurus. Results indicated that assemblage composition and structure differed significantly by season, likely influenced by temperature. However, within each season, the fish habitat use pattern at both the assemblage and species-specific level generally failed to support our working null hypothesis. Species-specific analyses revealed that, for most species and life-stages examined, nocturnal abundance either did not change with distance or increased with distance from the mangrove-seagrass ecotone. Our results suggest that analyses where taxa are grouped to report overall patterns may have the potential to overlook significant species- and stage-specific variation. For fishes known to make nocturnal migrations, we recommend nocturnal sampling to determine habitat utilization patterns, especially when inferring nursery value of multiple habitats or when estimating fish production.

Shining a light on fish at night: an overview of fish and fisheries in the dark of night, and in deep and polar seas

Article

Apr 2017
B MAR SCI

In aquatic environments, what one observes during the day can differ substantially by night. The species composition and associated ecological processes that occur during the day are often different than night. In polar seas and at great depths, " night " can span, months, years, and beyond. Teleosts and elasmobranchs have evolved unique sensory and behavioral modalities for living in darkness. As a consequence, fishers have adopted unique strategies for exploiting fish at night or in dark systems. We propose that neglecting the night has led to an incomplete understanding of aquatic organismal ecology, population/community dynamics, and ecosystem function with consequences for fisheries conservation management. To address this knowledge gap and stimulate the exchange of new data and ideas on behaviors, patterns, and processes relating to fish and fisheries in darkness, Fish at Night: an International Symposium was held in Miami, Florida (USA), from 18 to 20 November, 2015. Here, we synthesize the findings from the symposium, providing an overview on the state-of-knowledge of fish studies in the dark, identifying critical information gaps, and charting a course for future research. We focus our commentary and synthesis on six areas: (1) nocturnal fish behavior and ecology; (2) fishing, fisheries, and enforcement; (3) deep and polar seas; (4) diel fish distribution and abundance comparisons; (5) methods for studying fish in darkness; (6) human threats to fish at night; and (7) larval fish at night. Taken together, we attempt to " shine a light " on fish at night, generating a greater interest and understanding of fishes and fisheries during darkness.

Influence of predation risk and food supply on nocturnal fish foraging distributions along a mangrove-seagrass ecotone

Article

Sep 2010

Diverse taxa from many systems must make tradeoffs between food and safety. However, few studies have examined the response of multiple fish species to food and predation risk at night across their foraging landscape. In Biscayne Bay, Florida (USA), we investigated the influences of food and predation risk on nocturnal habitat use of gray snapper, bluestriped grunt and seabream along a distance gradient spanning from the mangrove-seagrass ecotone to 120 m offshore. Seine and submerged vegetation sampling were used to determine the distribution of fishes and their food resources. Tethering experiments were used to explore gradients in predator encounter rates. We used these data to test the following a priori predictions of fish distributions relative to food and risk as generated from foraging theory: (1) fishes will be distributed in proportion to their food supply (i.e. ideal free distribution, IFD); or (2) fishes will avoid high-risk areas such that their abundances will be lower than predicted by food resources in high-risk habitats (i.e. food-risk tradeoff). Results indicated that none of the fishes were distributed according to IFD. Seabream and gray snapper avoided foraging close to shore, where their food was abundant, but risk was highest. Bluestriped grunt responses to spatial variation in food supply and risk were less clear; they appeared to forage randomly across the distance gradient. Our results suggest that fish generally avoid the risky mangrove-seagrass ecotone, but responses to variation in food and risk are species-specific and may be dependent on specific anti-predator tactics or influenced by factors we did not measure.

Mangrove or mudflat: Prioritising fish habitat for conservation in a turbid tropical estuary

Article

Apr 2020

Mangrove habitats are typically the focus of conservation efforts in tropical estuaries because their structural complexity is thought to support greater biodiversity and nursery function than unvegetated habitats. However, evidence for this paradigm has been equivocal in turbid tropical estuaries where unvegetated mudflats are also highly productive. The present study compared the community composition, biodiversity, nursery-role and commercial fish biomass in two mangrove habitats and one mudflat habitat in the Gulf of Paria, Trinidad. A total of 12 705 fishes, comprising 63 species from 26 families, were sampled in mangrove creeks, seaward mangrove fringe and the subtidal margin of an intertidal mudflat from June 2014 to June 2015. The composition of the creek and mudflat communities were distinct, while the mangrove fringe community resembled the mudflat more than it did the mangrove creeks. Mean species richness (MSR), total species richness (TSR) extrapolated from species accumulation curves, and juvenile species richness (JSR) were significantly greater in the mudflat (MSR = 11.4 ± 1.0; TSR = 75 ± 14; JSR = 9.1 ± 0.8) than mangrove creeks (MSR = 9.0 ± 0.5; TSR = 49 ± 3; JSR = 6.1 ± 0.4) and the seaward mangrove fringe (MSR = 6.4 ± 0.7; TSR = 58 ± 14; JSR = 5.2 ± 0.4). Meanwhile, Shannon Weiner diversity, juvenile fish abundance and commercial fish biomass were comparable between habitats. These findings caution against the generalisation that mangroves are the most important habitat for fishes in turbid tropical estuaries. There is now a growing body of evidence that mudflats warrant consideration as important repositories of biodiversity and nursery function for juvenile fishes.

Mangrove or mudflat: prioritising fish habitat for conservation in a turbid tropical estuary

Thesis

Sep 2019

Guy Marley

Mangrove habitats are typically the focus of conservation efforts in tropical estuaries because their structural complexity is thought to support greater biodiversity and nursery function than unvegetated habitats. However, evidence for this paradigm has been equivocal in turbid tropical estuaries where unvegetated mudflats are highly productive. The present study compared the community composition, biodiversity, nursery-role and commercial fish biomass in two mangrove habitats and one mudflat habitat in the Gulf of Paria, Trinidad. A total of 12,005 fishes, comprising 63 species from 26 families, were sampled in mangrove creeks, seaward mangrove fringe and a subtidal mudflat from June 2014 to June 2015. The composition of the creeks and mudflat communities were distinct, while the mangrove fringe community resembled the mudflat more than it did the mangrove creeks. Mean species richness (MSR) and total species richness (TSR) extrapolated from species accumulation curves were significantly greater in the mudflat (MSR=11.4±1.0; TSR=75±14) than mangrove creeks (MSR=9.0±0.5; TSR=49±3) and the seaward mangrove fringe (MSR=6.4±0.7; TSR=58±14). Simpson’s diversity index, juvenile fish abundance and commercial fish biomass were comparable between habitats. However, biomass of commercially important juveniles was higher in the mudflat. Our findings caution against the generalisation that mangroves are the most important habitat for fishes in turbid tropical estuaries. There is now a growing body of evidence that mudflats warrant consideration as important repositories of biodiversity and nursery function for juvenile fishes.

Trophic Interactions in Coastal and Estuarine Mangrove Forest Ecosystems

Article

Dec 2011

Mangrove habitats are among the most productive ecosystems on the Earth. Their low vegetational diversity belies a remarkable richness of associated species and trophic interactions. This contribution summarizes what is known about these interactions. Information on interaction strengths, top-down versus bottom-up control, and the consequences of species interactions for community structure is only available for a few systems. At a more fundamental level, our understanding of the relative contributions of different sources of primary productivity and the patterns and mechanisms of their exploitation by herbivores, detritivores, and deposit feeders remains quite limited. Even less is known about the movement of carbon, nitrogen, and other elements through mangrove food webs to higher trophic levels. Long-standing paradigms asserting minimal consumption of living plant tissues by herbivores and the paramount role of mangrove detritus as fuel for secondary production of crustaceans and fish are being challenged by data gathered with newer methodologies, most notably, stable isotope analysis. Much remains to be learned about the role of mangroves as nurseries for juvenile life history stages and the trophic links between mangroves and neighboring ecosystems. Ongoing and future investigations of these processes that employ a balanced mix of quantitative observation and field experiments promise to generate exciting new insights about mangrove community and ecosystem processes, and at the same time inform general food-web theory.

Using artificial illumination to survey nocturnal reef fish

Article

Sep 2013
FISH RES

Effects of three different light wavelengths (blue, red and white) were assessed on the composition, abundance and behaviour of nocturnal fish at the Houtman Abrolhos Islands, Western Australia. The effects of fishing were also considered by further examining the combined effects of lighting and fishing (open vs. closed areas). Data were collected using baited remote underwater stereo-video systems (stereo-BRUVs), which were equipped with red (620–630 nm), white (550–560 nm) or blue (450–465 nm) lights. The total number of individuals, relative abundance of fish and assemblage composition differed under each lighting condition and fishing status. The greatest number of individuals was observed on samples illuminated by red lights (43% of all individuals surveyed). The species Apogon doederleini, Gymnothorax woodwardi, and Pempheris klunzingeri were each more abundant and spent longer in the field of view of the cameras using red lights. In contrast to white and blue light, the wavelength of red light is thought to be beyond the visual sensitivity of these fish species, and may not have affected their behaviour. The heavily targeted species, Pagrus auratus, were twice as abundant on stereo-BRUVs illuminated by blue lights and white lights than on red lights, but only in areas closed to fishing. This higher abundance on blue and white lights may have been due to the attraction of baitfish to these lights. In addition to the effects of lighting, clear effects of fishing were noted on nocturnal populations of P. auratus. Light wavelength can influence observations and measurements made of a nocturnal fish assemblage, and therefore careful consideration of choice of light wavelength should be made for nocturnal studies using artificial illumination on stereo-BRUVs.

The Influence of Body Size on the Ecology of Coastal Fish Predators in The Bahamas

Thesis

Nov 2011

Caroline Hammerschlag-Peyer

Body size is a fundamental structural characteristic of organisms, determining critical life history and physiological traits, and influencing population dynamics, community structure, and ecosystem function. For my dissertation, I focused on effects of body size on habitat use and diet of important coastal fish predators, as well as their influence on faunal communities in Bahamian wetlands. First, using acoustic telemetry and stable isotope analysis, I identified high variability in movement patterns and habitat use among individuals within a gray snapper (Lutjanus griseus) and schoolmaster snapper (L. apodus) population. This intrapopulation variation was not explained by body size, but by individual behavior in habitat use. Isotope values differed between individuals that moved further distances and individuals that stayed close to their home sites, suggesting movement differences were related to specific patterns of foraging behavior. Subsequently, while investigating diet of schoolmaster snapper over a two-year period using stomach content and stable isotope analyses, I also found intrapopulation diet variation, mostly explained by differences in size class, individual behavior and temporal variability. I then developed a hypothesis-testing framework examining intrapopulation niche variation between size classes using stable isotopes. This framework can serve as baseline to categorize taxonomic or functional groupings into specific niche shift scenarios, as well as to help elucidate underlying mechanisms causing niche shifts in certain size classes. Finally, I examined the effect of different-sized fish predators on epifaunal community structure in shallow seagrass beds using exclusion experiments at two spatial scales. Overall, I found that predator effects were rather weak, with predator size and spatial scale having no impact on the community. Yet, I also found some evidence of strong interactions on particular common snapper prey. As Bahamian wetlands are increasingly threatened by human activities (e.g., overexploitation, habitat degradation), an enhanced knowledge of the ecology of organisms inhabiting these systems is crucial for developing appropriate conservation and management strategies. My dissertation research contributed to this effort by providing critical information about the resource use of important Bahamian fish predators, as well as their effect on faunal seagrass communities.

Ecofisiologia e relações tróficas de elasmobrânquios: biomarcadores como ferramentas para conservação

Thesis

Full-text available

Apr 2023

Bianca Rangel

Dada a elevada diversidade nas estratégias de história de vida, os elasmobrânquios (tubarões e raias) tornam-se interessantes modelos para o estudo de relações entre a fisiologia e interações ecológicas no ambiente marinho. Embora os esforços para a conservação dos elasmobrânquios, que é atualmente o segundo grupo de vertebrados mais ameaçado do planeta, tenha estimulado um aumento no número de estudos sobre os padrões ecológicos e impactos antrópicos, pouco ainda se sabe sobre sua fisiologia. Assim, nesta tese de doutorado foram investigadas as variações fisiológicas sazonais e espaciais associadas ao estágio de vida e comportamento de tubarões de diferentes histórias de vida, utilizando múltiplas ferramentas não-letais para fornecer uma melhor compreensão dos padrões energéticos e reprodutivos, além de uma base fisiológica que ajude a prever os efeitos de distúrbios ambientais nos tubarões. O capítulo 1 aborda as variações inter- e intraespecíficas na ecologia nutricional de tubarões de diferentes estratégias de história de vida em um sistema insular oceânico protegido, o Arquipélago de Fernando de Noronha. Foram abordados também as variações nos padrões de dieta e condição nutricional e metabólica relacionados à reprodução de fêmeas de tubarões-tigre Galeocerdo cuvier (capítulo 2) e machos de tubarões-lixa Ginglymostoma cirratum e tubarões-galha-preta Carcharhinus limbatus (capítulo 3). Os capítulos 4, 5 e 6 abordam os efeitos da vida urbana na condição nutricional e padrões alimentares de tubarões com diferentes estilos de vida, o tubarão-lixa, o tubarão-galha-preta e o tubarão-tigre, respectivamente. Os resultados mostraram que a influência da urbanização na qualidade da dieta dos tubarões parece ser mais pronunciada em espécies sedentárias, como o tubarão-lixa, quando comparado com espécies mais ativas. Por fim, o capítulo 7 trouxe uma abordagem inédita na pesquisa de tubarões, combinando múltiplos marcadores fisiológicos com informações obtidas através de ultrassonografia e da telemetria acústica passiva para entender relações entre os aspectos fisiológicos e comportamentais de tubarões-tigre expostos ao turismo de alimentação. Os resultados demonstraram que o estágio de vida, a regulação endócrina e a condição nutricional influenciam e/ou são influenciadas pelo tempo que os tubarões passam interagindo com o turismo de alimentação. Em conjunto, os resultados mostraram que os biomarcadores nutricionais, reprodutivos e metabólicos utilizados nesta tese fornecem uma poderosa ferramenta para descrever padrões ecológicos complexos dos tubarões, especialmente quando combinados com outras tecnologias para rastreamento da movimentação e identificação do estágio reprodutivo dos tubarões.

Residency and Fine-scale Habitat Use of Juvenile Goliath Grouper ( Epinephelus Itajara ) in a Mangrove Nursery

Article

Full-text available

Apr 2023
B MAR SCI

The Atlantic goliath grouper ( Epinephelus itajara ) is the largest grouper species in the Atlantic and exhibits high site fidelity and limited range of movement. By 1990, the goliath grouper population in US waters had declined approximately 95% relative to unfished levels, leading to a harvest ban in 1990. Since then, the south Florida population has grown but the magnitude of recovery remains unknown due to uncertainties about life history characteristics. However, despite these unknowns, the state of Florida approved a limited recreational harvest of goliath grouper. In 2021, fine-scale habitat use of three juvenile goliath grouper was investigated using acoustic telemetry and a positioning solver. All three individuals exhibited high site fidelity as well as a diel habitat use pattern, utilizing seagrass habitat during the night and mangrove habitat during the day. Fine-scale acoustic telemetry provides insight into not only habitat use, but broader habitat preferences as well. This study illustrates the need to consider deep seagrass-dominated channels lined with red mangroves when protecting juvenile goliath grouper populations within Florida Bay, especially as the population is opened to harvest.

Urban living influences the nutritional quality of a juvenile shark species

Article

Feb 2021
SCI TOTAL ENVIRON

The field of marine urban ecology is a nascent, but growing area of research. An understanding of how urbanization may alter the diets and nutrition of marine species living in urbanized coastal habitats is limited. In the present study, we investigated the influence of urbanization on dietary patterns and nutritional quality of the nurse shark Ginglymostoma cirratum, a coastal epibenthic mesopredator. We tested the hypothesis that sharks sampled in urbanized areas (hereafter, ‘urban sharks’) would exhibit lower nutritional quality than individuals sampled in adjacent, but more pristine areas (hereafter ‘non-urban sharks’). To accomplish this, we compared plasma fatty acid profiles of juvenile nurse sharks in proximity to Miami, a large coastal city, within Biscayne Bay, Florida. Results revealed that urban sharks contained higher levels of plasma saturated and bacterial fatty acids compared to non-urban sharks. Urban sharks also exhibited lower proportions of essential fatty acids (i.e., highly unsaturated fatty acids, HUFAs), mainly due to low contributions of omega-6 HUFAs. These results suggest that urban sharks consumed lower-quality food resources than conspecifics in less impacted areas. The apparent poor nutritional quality of prey consumed by shark living in urban areas may have several long-term consequences on their health and growth.

Genetic relationships and hybridization among three western Atlantic sparid species: sheepshead (Archosargus probatocephalus), sea bream (A. rhomboidalis) and pinfish (Lagodon rhomboides)

Article

Full-text available

Feb 2020
CONSERV GENET

Three species of sparids in the western Atlantic, sheepshead (Archosargus probatocephalus), sea bream (A. rhomboidalis), and pinfish (Lagodon rhomboides), share overlapping habitats, spawning seasons, and spawning grounds, providing opportunities for interaction among these species. Three regions of mitochondrial DNA and three nuclear DNA intron sequences were used to construct the genetic relationships among these species. The results showed that these species are closely related, suggesting the presence of soft polytomy with sheepshead and western Atlantic sea bream as sister species. However, western Atlantic sea bream and pinfish are equally divergent from sheepshead. We used a suite of 18 microsatellite markers to verify the occurrence of hybridization, identify the parental types, and evaluate the filial-generation status of 36 individuals morphologically identified as hybrids from the Indian River Lagoon system, in Florida. The 36 putative hybrids were analyzed with a reference group of 172 western Atlantic sea bream, 232 pinfish, and 157 sheepsheads and were all genetically determined to be F1 of sheepshead and western Atlantic sea bream with very little indication or no introgressive hybridization among the 172 reference specimens of western Atlantic sea bream. Hybridization was asymmetric, with western Atlantic sea bream males crossing with sheepshead females. Hybrids were first observed in the Indian River Lagoon in 2005, after the western Atlantic sea bream had become common there, in the 1990s. Their occurrence could be associated with unique features of the Indian River Lagoon that bring the two species together or with recent anthropogenic changes in this system. Further study is needed to determine the causes and long-term effects of the recurrent production of F1 hybrids and the degree of their sterility in the Indian River Lagoon.

Effects of a no-take reserve on mangrove fish assemblages: incorporating seascape connectivity

Article

Jul 2020

No-take reserves (NTRs) have been effective at conserving fish assemblages in tropical systems such as coral reefs, but have rarely been evaluated in turbid tropical estuaries. The present study evaluated the effect of a mangrove NTR on the conservation of juvenile fish abundance, commercial fish biomass and biodiversity at the assemblage level; and the abundance of juveniles, target and non-target adults at the family level. The evaluation incorporated one aspect of seascape connectivity - proximity to the sea, or in this case, the Gulf of Paria. Linear mixed models showed that the NTR had a positive effect only on species richness at the assemblage level. However, juvenile fish abundance, commercial fish biomass, taxonomic distinctness and functional diversity were not enhanced in the NTR. The inclusion of connectivity in these models still failed to identify any positive effects of the NTR at the assemblage level. Yet, there were significant benefits to juvenile fish abundance for 5 of 7 families, and for one family of non-target adults. Possible explanations for the limited success of the NTR to fish assemblages include failing to account for the ecology of fish species in NTR design, the drawbacks of ‘inside-outside’ (of the NTR) experimental designs, and the fact that fishing does not always impact non-target species. It is important to recognise that mangrove NTRs do not necessarily benefit fish assemblages as a whole, but that finer scale assessments of specific families may reveal some of proclaimed benefits of NTRs in tropical estuaries.

Rough Around the Edges: Lessons Learned and Future Directions in Marine Edge Effects Studies

Article

Full-text available

Dec 2019

Purpose of Review After several decades of research on edge effects in marine habitats, we still have little understanding of how organisms respond to marine ecotones, and methodological gaps appear to be limiting our progress. Using recent literature (2010–2018), we synthesized responses and processes of organisms across several marine habitats. Specifically, we examined the uniformity of studies across biogenic habitats, the scales selected for exploring edge effects, the experimental approaches used, and the confounding influences that muddle our interpretation of results. Recent Findings The majority of edge effect studies are still conducted in seagrass systems and focused on response patterns. We found that the majority of studies were equally likely to report an increase, decrease, neutral, or equivocal effect depending on the context of the organism or habitat. Additionally, only a single measure, or a few related responses, is assessed and causal mechanisms are rarely tested. We note that most studies quantitatively defined an edge habitat as a linear distance from a habitat boundary (e.g., < 1 m, < 5 m), but the distances were not usually scaled to the size, trophic level, or mobility of focal organisms. Summary We provide a conceptual diagram as a roadmap for researchers for navigating the myriad influences that affect floral and faunal responses to marine habitat edges. Future efforts should seek to move beyond mensurative searches, explicitly incorporate potentially confounding variables, and more consistently test putative causal factors when known or hypothesized. Additionally, we advise expanding research on habitat types other than seagrasses (e.g., mangroves, shellfish, corals) and adjusting observational scales to more appropriately match mechanisms. Ultimately, we should move beyond pattern description, repeated in a limited subset of nearshore habitats, and toward a quantitative understanding of the processes acting in these unique and potentially impactful marine ecotones.

Abundancia y diversidad de la ictiofauna en la Reserva de la Biósfera Los Petenes, Campeche, México: asociaciones con los ciclos nictimerales y las épocas climáticas Abundance and diversity of fishes in Los Petenes Biosphere Reserve, Campeche, Mexico: nycthemeral cycles and climatic seasons interrelationships

Article

Full-text available

May 2017

In the Mexican state of Campeche, the marine littoral portion of Los Petenes Biosphere Reserve (RBLP), integrates several ecological components such as the fish community as the more diverse and abundant aquatic macrofauna. The coastal marine fish structure and function is conditioned by the comprehension of the environmental dynamic in different scale. In the present study, nycthemeral samplings were carried out in three moments of year 2009 in a site located in the central region of the RBLP with the objective of describing environmental patterns and changes in abundance and diversity of the ichthyofauna and discuss their associations with the day-night cycles and with the times of cold fronts “nortes”, dry and rain. The results show significant differences in the environmental behavior between the three climatic seasons but not between the day hours and the night hours. 31 species were identified, including the families Haemulidae, Sparidae, Lutjanidae, Sciaenidae, Monacanthidae and Tetraodontidae by their species richness. Twelve species were identified dominant being the most abundant Haemulon plumierii, Lagodon rhomboides, Orthopristis chrysoptera and Eucinostomus gula. The highest abundance was recorded in “nortes” climatic season and the lowest in “dry” one and in the latter ones were observed the greatest differences between day and night. The dominant species were associated in two groups that match by its abundance in hours of the day and of the night and with environmental variability.

Patterns of resource use and isotopic niche overlap among three species of sharks occurring within a protected subtropical estuary

Article

Full-text available

Sep 2017
AQUAT ECOL

Predation is one of the most fundamental and unifying concepts in ecology, and we are beginning to obtain a more complete understanding of how predators drive community structure and ecosystem function through their impacts on prey. We know considerably less about how predators affect each other through intraguild interactions, which is surprising considering predators often occur simultaneously and may compete for resources while avoiding being killed themselves. In the present study, we examined aspects of inter- and intra-specific resource use among three species of large-bodied predatory sharks (blacktip, bull, lemon) co-occurring within a subtropical, protected bay in the southeastern USA. Specifically, we inferred relative trophic position, isotopic niche overlap, and patterns of resource use of sharks using stable isotope analysis of carbon-13 and nitrogen-15 from blood and fin cartilage samples. We also combined these approaches with estimates of abundance and occurrence from empirical shark surveys to consider whether these species may exhibit resource partitioning in space and time. We found that all three species overlapped in space, and there was some isotopic niche overlap between the species. We also found evidence of temporal isotopic niche stability, suggesting that co-occurring shark species may compete for available prey resources, but individuals of those species may have similar patterns of resource use over time. We discuss our findings as they relate to the ecologies of the species in question and how sound conservation and management of ecosystems can allow for predator diversity, sympatry, and stable use of resources at the top of the food chain.

Life History Profiles Outline ECOSPECIES: Gray Snapper Title: Species Profile Gray Snapper (Lutjanus griseus)

Technical Report

Full-text available

Jun 2014

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.

Ecotone Effects on Seagrass and Saltmarsh Habitat Use by Juvenile Nekton in a Temperate Estuary

Article

Full-text available

Oct 2014
ESTUAR COAST

While considering important juvenile fish habitats individually, both seagrass and saltmarsh are often highly connected with other subtidal and intertidal habitats. As a result, juvenile fishes and crustaceans may utilize multiple habitats across tidal, diel, or seasonal cycles in a manner that makes interhabitat proximity an important driver of fish distribution and community composition. In this context, we examined the importance of seagrass (Zostera marina and Halodule wrightii) and saltmarsh (Spartina alterniflora) habitat characteristics in driving fish and crustacean catch rates and community composition in a temperate, polyhaline-euhaline, estuary. We found that habitats with highly connected seagrass and saltmarsh vegetation exhibited higher average catch rates of many recreationally and commercially valuable fish and crustacean species, as well as overall nekton catch rates and Shannon diversity (H), than habitats composed of either seagrass or saltmarsh habitat alone. Nekton-habitat associations varied temporally, showing strong seasonal trends which were potentially indicative of temporal shifts in relative habitat value. Catch rates of numerous recreationally and commercially targeted species were correlated with patch-scale variables, particularly seagrass canopy height, water temperature, and depth; however, regression analysis indicated that habitat type was more powerful in predicting overall nekton catch rates and Shannon diversity (H). We conclude that emergent properties (i.e., those operating at 10–100s m) are important drivers of nekton distributions among and within habitats. Considering the spatial and temporal scales at which humans are encroaching on estuarine ecosystems, our findings highlight the need for investigating organism-habitat associations at expanded spatial scales, as well as the need to adopt fishery and coastal management plans that consider habitat characteristics at multiple spatial scales to account for interhabitat connectivity.

Augmentation of French grunt diet description using combined visual and DNA-based analyses

Article

Full-text available

Jan 2012

Trophic linkages within a coral-reef ecosystem may be difficult to discern in fish species that reside on, but do not forage on, coral reefs. Furthermore, dietary analysis of fish can be difficult in situations where prey is thoroughly macerated, resulting in many visually unrecognisable food items. The present study examined whether the inclusion of a DNA-based method could improve the identification of prey consumed by French grunt, Haemulon flavolineatum, a reef fish that possesses pharyngeal teeth and forages on soft-bodied prey items. Visual analysis indicated that crustaceans were most abundant numerically (38.9%), followed by sipunculans (31.0%) and polychaete worms (5.2%), with a substantial number of unidentified prey (12.7%). For the subset of prey with both visual and molecular data, there was a marked reduction in the number of unidentified sipunculans (visual - 31.1%, combined - 4.4%), unidentified crustaceans (visual - 15.6%, combined - 6.7%), and unidentified taxa (visual - 11.1%, combined - 0.0%). Utilising results from both methodologies resulted in an increased number of prey placed at the family level (visual - 6, combined - 33) and species level (visual - 0, combined - 4). Although more costly than visual analysis alone, our study demonstrated the feasibility of DNA-based identification of visually unidentifiable prey in the stomach contents of fish.

Exploring ‘knowns’ and ‘unknowns’ in tropical seascape connectivity with insights from East African coral reefs

Article

Jul 2012

Diel movements of fishes linked to benthic seascape

Article

Full-text available

Jan 2011
MAR ECOL-PROG SER

Many common fishes associated with Caribbean coral reef ecosystems use resources from more than 1 patch type during routine daily foraging activities. Few studies have provided direct evidence of connectivity across seascapes, and the importance of benthic seascape structure on movement behavior is poorly known. To address this knowledge gap, we coupled hydro-acoustic technology to track fish with seafloor mapping and pattern analysis techniques from landscape ecology to quantify seascape structure. Bluestriped grunts Haemulon sciurus and schoolmaster snapper Lutjanus apodus were tracked over 24 h periods using boat-based acoustic telemetry. Movement pathways, and day and night activity spaces were mapped using geographical information system (GIS) tools, and seafloor structure within activity spaces was mapped from high-resolution aerial photography and quantified using spatial pattern metrics. For both fish species, night activity spaces were significantly larger than day activity spaces. Fish exhibited a daytime preference for seascapes with aggregate coral reef and colonized bedrock, then shifted to night activity spaces with lowercomplexity soft sediment including sand, seagrass, and scattered coral/rock. Movement path complexity was negatively correlated with seascape complexity. This demonstrates direct connectivity across multiple patch types and represents the first study to apply quantitative landscape ecology techniques to examine the movement ecology of marine fish. The spatially explicit approach facilitates understanding to the linkages between biological processes and the heterogeneity of the landscape. Such studies are essential for identifying ecologically relevant spatial scales, delineating essential fish habitat and designing marine protected areas.

Sources of primary production supporting food webs in an arid coastal embayment

Article

Full-text available

Aug 2012

Penaeid shrimp can be useful ecological indicators of linkages between shallow tropical coastal habitats, acting as integrators of carbon and nitrogen sources due to their generalist feeding habits and their mobility between habitats and with tidal cycles. In the current study, the contribution of mangrove, seagrass and microbial mat to the nutrition of two penaeid shrimp species, Penaeus semisulcatus and Metapeneus ensis, in a shallow arid embayment in the Arabian Gulf was assessed through a combination of analysis of stomach contents and dual carbon and nitrogen stable isotope signatures. Shrimp tissue stable isotope signatures identified seagrass as a major source of carbon and nitrogen for both species, contributing 21–38 % (1–99 ‰). Microbial mat was also detected as a significant nutritional source for early-stage Metapenaeus affinis postlarvae (1–27 %). However, mangroves were not identified as a significant source, with the range of results including the possibility of a zero contribution. Moreover, the greatest possible contribution of mangroves as source of carbon was less than for the other primary producers. This may be due the high salinity and wide temperature range limiting mangrove productivity as well as the low export of dissolved and particulate organic material out of the mangroves due to low rainfall.

Mangrove Shoreline Fish Assemblages of Oleta River State Park: Baseline Conditions in an Urban System

Article

Oleta River State Park (ORSP), located in North Miami-Dade County is known as the most highly urbanized State Park in all of Florida. The present study was conducted as part of an ongoing seasonally-resolved survey of fish utilization of the mangrove shorelines of Biscayne Bay. Previous Unit Management Plans published by the Division of Recreation and Parks have lacked information concerning the park?s prominent mangrove forests along with its icthyofauna. The main purpose of this thesis was to provide a baseline characterization of the mangrove-fish assemblages and microhabitat trends of ORSP, against which future changes in and around the Park can be gauged. Fish assemblages inhabiting the mangrove shorelines were examined using a visual ?belt-transect? census method over 11 consecutive seasons. Microhabitat variables including salinity, water temperature, water depth, water clarity and distance from Baker?s Haulover Inlet were examined for possible correlations with fish metrics. Several significant differences were evident in the taxonomic richness (number of taxa per unit area) and densities of the five most abundant taxa within the shoreline habitats in terms of seasonal variation and microhabitat variable distribution along the river. Taxonomic richness was typically greater in survey sites located closer to Baker?s Haulover Inlet. Oleta River?s mangrove shoreline fish assemblages appear to reflect (1) proximity of the mangroves that they occupy to Baker?s Haulover Inlet; (2) temperature regime along the shoreline; and (3) the salinity gradient found within the river. Fish assemblage and microhabitat information collected here could serve as a ?baseline? in future investigations of the effects of further urbanization or the effects of other anthropogenic changes to Oleta River and its mangrove habitat, including possible changes to freshwater flow associated with the Comprehensive Everglades Restoration Plan.

A Hypothesis-Testing Framework for Studies Investigating Ontogenetic Niche Shifts Using Stable Isotope Ratios

Article

Full-text available

Nov 2011
PLOS ONE

Ontogenetic niche shifts occur across diverse taxonomic groups, and can have critical implications for population dynamics, community structure, and ecosystem function. In this study, we provide a hypothesis-testing framework combining univariate and multivariate analyses to examine ontogenetic niche shifts using stable isotope ratios. This framework is based on three distinct ontogenetic niche shift scenarios, i.e., (1) no niche shift, (2) niche expansion/reduction, and (3) discrete niche shift between size classes. We developed criteria for identifying each scenario, as based on three important resource use characteristics, i.e., niche width, niche position, and niche overlap. We provide an empirical example for each ontogenetic niche shift scenario, illustrating differences in resource use characteristics among different organisms. The present framework provides a foundation for future studies on ontogenetic niche shifts, and also can be applied to examine resource variability among other population sub-groupings (e.g., by sex or phenotype).

Minimum multipliers for fishery offsets in marine habitats vary depending on the no net loss goal

Article

Aug 2023
BIOL CONSERV

Measuring mutual movements, mixing, and mingling among multiple mangrove bays by an important estuarine sea bream (Archosargus rhomboidalis)

Article

Full-text available

Feb 2021

Quantifying the spatial and temporal aspects of fish residency is needed to understand energy transfer, habitat function, contaminant exposure, and effective design of MPAs in estuarine systems. The spatial and temporal movements of 19 sea bream (Archosargus rhomboidalis), an ecologically important species in mangrove estuaries of the western Atlantic, were investigated in multiple bays on a Caribbean Island over two years using surgically implanted acoustic transmitters. Fish were almost continuously monitored (residency index 96–100%) by an array of hydrophones during the 11–13 month battery-life of their transmitters. Individual fish utilized small core areas (mean = 9.8 ha during daytime and 11.0 ha at night), displayed daily site fidelity (mean = 57% overlap in day night core area), showed no evidence of an ontogenetic increase in core habitat size, and many exhibited a change in the bays utilized during winter months which is coincident with suspected spawning. Fish captured from the same bay generally occupied the same spaces within the study area, and in similar proportions, compared to fish captured in adjacent bays. Fish from different bays did not mix and wander throughout the ecosystem even though it is all suitable habitat and is used by different groups of localized individuals. This similarity of occupancy patterns is limited to the spatial scale of bays and temporal scales of weeks or months. When considered at the resolution of individual receivers and hourly time steps, most fish are not in close proximity to one another for the vast majority of the time. Although some pairs of fish had as many as 84% of their hourly detections on the same receivers in the month after tagging, they gradually spent less time near each other, even though their overall pattern of movements was consistent at the scale of whole bays. This highlights the importance of examining movements of fish on multiple spatial scales and time-intervals to understand their interactions.

Diel Variability and Influence of Artificial Light on Fish and Macroinvertebrate Communities in Gulf of Mexico Seagrass Beds Diel Variability and Influence of Artificial Light on Fish and Macroinvertebrate Communities in Gulf of Mexico Seagrass Beds

Article

Dec 2020

Seagrasses are productive habitats that support diverse communities of economically and ecologically important fishes and macroinvertebrates. However, most seagrass faunal assessments are conducted only during daylight hours. Here, we documented diel patterns in seagrass-associated fish and macroinvertebrate community structure in seagrass near Seahorse Key, Florida (USA). Artificial light is prevalent in many coastal areas and may influence day/night assemblages; therefore, we added lights to the natural environment to get a better understanding of its effect on community composition. Seagrass inhabitants were quantified using 25-m seine transects during different diel periods (day or night) and in areas where light was manipulated to mimic light pollution (artificial + natural light or natural light). Results suggest that the magnitude of diel effects exceeded that of light addition. While total abundance was similar between day and night, communities did change, with Lagodon rhomboides (Pinfish) dominating day samples and Farfantepenaeus duorarum (pink shrimp) most abundant at night. Other fishes such as Orthopristis chrysoptera (Pigfish) and Strongylura notata (Needlefish) had higher catches during the day, while invertebrates such as Callinectes sapidus (blue crab) and Palaeomonetes spp. (grass shrimp) were more prominent at night. In addition to the differences in abundance and community structure, we also identified diel differences in sizes for some species. No clear patterns were observed with the short-term addition of artificial light. This research highlights the role of diel variability in seagrass communities and suggests that diel movement of organisms may represent an important conduit for the transfer of energy to adjacent habitats.

Habitat Use Patterns of Coastal Shark Species in Relation to Boat Activity along an Urban Marine Gradient

Thesis

May 2020

The effects of boat activity on various aspects of fish biology and ecology have been widely studied in the past few decades. However, these studies primarily focused on teleost fish species and not elasmobranchs. The goal of this study was to determine if there was a negative relationship between boat activity and the habitat use of three coastal shark species (bull (Carcharhinus leucas), nurse (Ginglymostoma cirratum), and great hammerhead (Sphyrna mokarran)) in Biscayne Bay, Florida - an area subject to intense boat activity (both commercial and recreational). According to past studies on marine mammals and teleost fish species, we expected sharks to present patterns of avoidance (reduced residency and activity space) during times and in areas of intense boat activity. Using aerial surveys and underwater recording stations, patterns of boat activity were quantified both spatially and temporally, while shark activity space and residency were determined using acoustic telemetry. Our results indicated that boat activity was more intense both on the weekends/holidays and closer to Miami Proper. However, there was no relationship between boat activity patterns and the activity space or residency of each species. These results may be explained by each species' hearing ability and how their detectable frequency range does not overlap with that produced by boat engines. Additionally, it is possible that the shark species in this area have habituated to the human activity and associated sound as demonstrated by a population of bottlenose dolphins (Tursiops truncates) in the same area. This study lays a foundation that future research can use to explore the relationship between boat activity and other vulnerable species as well as expand our current understanding of the relationship between sharks and urbanization.

Global affiliation of juvenile fishes and invertebrates with mangrove habitats

Article

Jan 2019
B MAR SCI

Mangroves are critical fish and invertebrate habitats, however, identifying to what degree species are affiliated to mangrove systems remains challenging. Here we outline and apply two quantitative and one qualitative method for assessing the degree of mangrove affiliation globally at a species level, based on habitat-specific fish and invertebrate species densities extracted from an exhaustive search of the literature, for mangroves and their associated coastal habitats. We assessed all 121 species for which we had ≥7 mangrove records and where data allowed, quantified the percentage contribution of mangroves to the summed species density across all habitats. We set the threshold for identifying a species as "highly mangrove-affiliated" as ≥70% relative density, and examined its validity by subjecting a subset of species either side of the threshold to a thorough review of evidence for mangrove affiliation in the peer reviewed literature. We found that 53 were highly mangrove-affiliated, including 24 fish and three invertebrate species from the Atlantic East Pacific, and nine fish and 15 invertebrate species from the Indo West Pacific ( n = 2 had global distributions). 36 of the 53 species are of value to artisanal, subsistence or commercial fisheries; 21 in the Atlantic East Pacific, and 13 in the Indo West Pacific. While this list of highly mangrove-affiliated species is far from complete due to data limitations, it represents the first attempt to undertake a global overview of highly mangrove-affiliated species, and a proof of concept for a quantitative and objective method of assessment.

Coastal Habitats of the Gulf of Mexico

Chapter

Full-text available

Jun 2017

Urbanization and industrial development pressures have seriously impacted coastal ecosystems, including vegetated intertidal and subtidal marine habitats such as barrier strands and associated wetlands and seagrasses. These ecosystems provide a suite of services including carbon storage, pollution and nutrient abatement, soil formation, fisheries support, and flood and storm protection. Emphasis has been placed on vegetated marine habitats that occur immediately adjacent to the Gulf of Mexico, including barrier islands and beaches, salt marshes and mangroves, seagrasses, intertidal and subtidal flats, and reed marshes at the mouth of the Mississippi River. These habitats, their depositional environments, and the ecology of their dominant flora and fauna are described within the context of major marine and terrestrial ecoregions. The information and analysis in this chapter should better enable effective management and restoration of coastal habitats in the Gulf as environmental change continues to alter their structure and function and reshape their associated biotic assemblages.

Quantifying the conservation value of seascape connectivity: A global synthesis

Article

Full-text available

Nov 2015
GLOBAL ECOL BIOGEOGR

Aim Connectivity structures populations, communities and ecosystems in the sea. The extent of connectivity is, therefore, predicted to also influence the outcomes of conservation initiatives, such as marine reserves. Here we review the published evidence about how important seascape connectivity (i.e. landscape connectivity in the sea) is for marine conservation outcomes. Location Global. Methods We analysed the global literature on the effects of seascape connectivity on reserve performance. Results In the majority of cases, greater seascape connectivity inside reserves translates into better conservation outcomes (i.e. enhanced productivity and diversity). Research on reserve performance is, however, most often conducted separately from research on connectivity, resulting in few studies (< 5% of all studies of seascape connectivity) that have quantified how connectivity modifies reserve effects on populations, assemblages or ecosystem functioning in seascapes. Nevertheless, evidence for positive effects of connectivity on reserve performance is geographically widespread, encompassing studies in the Caribbean Sea, Florida Keys and western Pacific Ocean. Main conclusions Given that research rarely connects the effects of connectivity and reserves, our thesis is that stronger linkages between landscape ecology and marine spatial planning are likely to improve conservation outcomes in the sea. The key science challenge is to identify the full range of ecological functions that are modulated by connectivity and the spatial scale over which these functions enhance conservation outcomes.

Sea turtle conservation and ecosystem-based management with a focus on green turtles (Chelonia mydas) and seagrass beds

Article

Jan 2010

Colette C C Wabnitz

Coral loss and fish guild stability on a Caribbean coral reef: 1974–2000

Article

Apr 2014

Data on reef substrate composition and fish guild structure was extracted from filmed underwater surveys conducted in 1974 and 2000 at a coral reef in the Florida Keys. During the course of this 26-year interval the reef underwent a dramatic (>75 %) loss of stony coral cover, particularly acroporids, accompanied by significant increases in turf algae, crustose-coralline algae, octocorals, and macroalgae. At the same time, marked changes occurred in the structure of a guild of large herbivorous reef fishes. Total abundance declined, and the relative abundance of constituent species and functional groups changed as well. In contrast, we recorded no change in any measure of structural stability in either of two carnivorous fish guilds (lutjanids, haemulids) that feed by night in off-reef habitats. These results are generally consistent with the hypothesis that coral loss differentially impacts functionally dissimilar groups of fishes, according to dependency on reef substrates for food and/or shelter. The persistence of sizeable herbivore populations along with the relatively low (

Factors affecting resource use variation in an abundant coastal fish predator, Lutjanus apodus, in a Bahamian wetland system predator

Article

Apr 2012
B MAR SCI

Studies of fishes' resource use reflect important ecological interactions, and provide insight into the structure of aquatic food webs. Individuals within species are often assumed to have an equivalent ecological role despite increasing evidence that among-individual variation in resource use within populations is common. Such intraspecific variation in resource use can be a result of ontogenetic-based diet shifts, differences in individual feeding behavior within age groups (i.e., individual specialization), and temporal variation in resource pools. We examined trophic interactions in schoolmaster, Lutjanus apodus (Walbaum, 1972), over multiple seasons and across size classes in a Bahamian wetland system. Using combined stable isotope and stomach content analyses, we found that, as with many other fishes, subadults fed at higher trophic levels than juveniles, likely because of a shift from feeding predominantly on lower trophic-level prey taxa (e.g., crabs) to higher trophic-level prey taxa (e.g., teleosts). Despite a considerable overlap in stable isotope values between subadults and juveniles, stable isotope and stomach content data suggest a switch from feeding predominantly within mangrove prop roots as juveniles to foraging increasingly in adjacent seagrass beds as subadults. Niche width and degree of individual dietary specialization varied among years, suggesting important levels of temporal variation. In sum, individual snapper do not use resources homogeneously, and we outline some of the factors, including predation risk, increase piscivory, and temporal differences in resource use, that underlie this variation.

Seasonal diet and feeding habits of juvenile fishes foraging along a subtropical marine ecotone

Article

Jun 2010

Few studies have examined seasonal diet variation and trophic relationships among fishes in shallow subtropical waters. We sampled consecutive wet and dry seasons within Biscayne Bay, Florida, USA, to examine seasonal diet and feeding habit variation in juvenile gray snapper Lutjanus griseus (GS), bluestriped grunt Haemulon sciurus (BSG), seabream Archosargus rhomboidalis (SB) and great barracuda Sphyraena barracuda (GB). We found significantly lower feeding intensity during the dry season compared to the wet, which is likely related to lower water temperatures during the former season. GS fed on a variety of fishes and crustaceans, while BSG fed primarily on caridean shrimps. SB fed on vegetation and GB was piscivorous. Seasonal shifts in major food resources generally did not correspond with changes in relative abundance of food supply. Seasonal population niche breadth differences were evident for GS, GB and BSG, but for SB niche breadth was similar between seasons. Based on seasonal food supply, population niche breadth values did not match basic foraging theory predictions, which state that niche breadth should expand as preferred food items become scarce. In GS, BSG and GB, individuals fed on a narrow subset of prey consumed by the population, revealing the existence of individual specialization. For these species, seasonal expansion in population niche breadth did not correspond to increased individual specialization, but rather via increased within-individual variation in resource use. Given the seasonal differences in feeding habits, it is important to incorporate seasonal variation when modeling trophodynamics of shallow subtropical systems or characterizing them as essential fish habitats.

Relative predation risk for fishes along a subtropical mangrove–seagrass ecotone

Article

Feb 2010

Many fishes shelter in mangrove habitats by day and forage mostly in seagrass beds by night. This pattern of diel habitat use has been attributed to a predator avoidance strategy, whereby predation risk is reduced by alternating between the cover afforded by prop-roots during the day and darkness at night. We employed a series of diel tethering experiments in Biscayne Bay (Florida, USA) to empirically examine whether relative predation pressure on fishes is lower at night than during the day and to compare relative predation pressure on fishes at different distances from the mangrove- seagrass ecotone. Pinfish Lagodon rhomboides ranging from 10 to 17 cm in total length were tethered during day and night at 10, 50, and 110 m from the mangrove-seagrass ecotone. Pinfish removal rates at night were twice as high as during the day, which contradicts the idea that darkness provides 'cover' during nocturnal foraging in seagrass. Predation losses were highest nearest the mangrove edge and decreased with increasing distance from shore. Our results agree with those of other tethering studies that marine ecotones, or transition zones between refuges and feeding sites, can be areas of high predation pressure for fishes.

Diel movements of fishes linked to benthic seascape structure in a Caribbean coral reef ecosystem

Article

Full-text available

Apr 2011
MAR ECOL-PROG SER

Many common fishes associated with Caribbean coral reef ecosystems use resources from more than 1 patch type during routine daily foraging activities. Few studies have provided direct evidence of connectivity across seascapes, and the importance of benthic seascape structure on movement behavior is poorly known. To address this knowledge gap, we coupled hydro-acoustic technology to track fish with seafloor mapping and pattern analysis techniques from landscape ecology to quantify seascape structure. Bluestriped grunts Haemulon sciurus and schoolmaster snapper Lutjanus apodus were tracked over 24 h periods using boat-based acoustic telemetry. Movement pathways, and day and night activity spaces were mapped using geographical information system (GIS) tools, and seafloor structure within activity spaces was mapped from high-resolution aerial photography and quantified using spatial pattern metrics. For both fish species, night activity spaces were significantly larger than day activity spaces. Fish exhibited a daytime preference for seascapes with aggregate coral reef and colonized bedrock, then shifted to night activity spaces with lower-complexity soft sediment including sand, seagrass, and scattered coral/rock. Movement path complexity was negatively correlated with seascape complexity. This demonstrates direct connectivity across multiple patch types and represents the first study to apply quantitative landscape ecology techniques to examine the movement ecology of marine fish. The spatially explicit approach facilitates understanding to the linkages between biological processes and the heterogeneity of the landscape. Such studies are essential for identifying ecologically relevant spatial scales, delineating essential fish habitat and designing marine protected areas.

Importance of mangroves and seagrass beds as nurseries for coral reef fishes in Tanzania

Thesis

Full-text available

Jan 2012

Ismael Kimirei

Contrasting habitat use of diurnal and nocturnal fish assemblages in temperate Western Australia

Article

Sep 2012
J EXP MAR BIOL ECOL

This study examined the diversity and relative abundance of fish species in six coastal habitats during the day and at night. Habitats included seagrass beds, Ecklonia macroalgal beds, other macrophytes, deep reef, rhodolith beds and sand. Surveys were conducted using baited remote underwater stereo-video systems, which at night were equipped with either white or red lights. Three research questions were examined; 1) do fish assemblages sampled during the day differ to those sampled at night across six inshore and near shore marine habitats? 2) Are patterns of habitat associations displayed by diurnal fishes maintained at night? 3) Do stereo-BRUVs sample different fish assemblages when equipped with red versus white lights?

Ecosystem equivalence and the ability to generalise: Insights from global consistencies in mangrove fish assemblages

Article

Aug 2012
MAR ECOL-PROG SER

Marcus Sheaves

It is common practice in ecology to extrapolate understanding of processes and functions from one example of an ecosystem to another. Valid extrapolation requires an assumption of ecosystem equivalence, i.e. that the different examples of the ecosystem are actually similar in regard to the understanding being extrapolated. I use the example of mangrove fish assemblages to assess ecosystem equivalence using data compiled from 76 studies from around the world. Although there were distinct fish faunal groups (FGs) in different areas of the world, there was evidence of underlying faunal equivalence. Mangrove fish comprised a restricted pool of 170 families, with 41 of those occurring in all 4 FGs. Whether studies only considered fish actually entering mangrove forests or included associated habitats was not an important factor for differentiating assemblages. This suggests that from a fish perspective, the mangrove ecosystem is defined at a whole-of-mangrove system level rather than the scale of the mangrove forest. There were notable differences among families that distinguished the different FGs, but these differences did not translate into functional differences. Although the results appear to provide a degree of validity for extrapolating understanding of processes and functions from one example of an ecosystem to another, this implied support must be set in the context of the limitations of the available data. In-depth evaluation of ecosystem equivalence is urgently needed because this untested assumption is central to the validity of every model or interpretation based on data from a distant location.

Assessing the overlap between the diet of a coastal shark and the surrounding prey communities in a sub-tropical embayment

Article

May 2011
J FISH BIOL

An elasmobranch survey of sub-tropical Hervey Bay, Australia, captured the slit-eye shark Loxodon macrorhinus at only one of three sites sampled. The dietary composition of this small shark species was compared to the prey communities within Hervey Bay to test whether prey availability was driving this observation. Dietary analysis of prey groups revealed that teleosts dominated the diet, per cent index of relative importance, % I(RI) (79·5%) and per cent geometric index of importance, % G(II) (52·7%), with shrimp-like invertebrates and cephalopods identified as the most important invertebrate prey groups. Baited remote underwater video (BRUV) used to sample prey communities at each site, demonstrated a highly diverse and significantly different community composition among the sites. There was no significant overlap between the diet of L. macrorhinus and any of the prey communities detected by BRUVs according to one-way analysis of similarities and the simplified Morisita index. Habitat electivity analysis revealed affinity of L. macrorhinus for the site with the highest water clarity (Secchi disc depth), opposing that of three other shark species. Overall, the results suggest that the distribution of L. macrorhinus is not driven by prey availability but other factors such as water clarity, predator avoidance or a reduction in interspecies competition.

Mangroves enhance the biomass of coral reef fish communities in the Caribbean

Article

Full-text available

Feb 2004
NATURE

Mangrove forests are one of the world's most threatened tropical ecosystems with global loss exceeding 35% (ref. 1). Juvenile coral reef fish often inhabit mangroves, but the importance of these nurseries to reef fish population dynamics has not been quantified. Indeed, mangroves might be expected to have negligible influence on reef fish communities: juvenile fish can inhabit alternative habitats and fish populations may be regulated by other limiting factors such as larval supply or fishing. Here we show that mangroves are unexpectedly important, serving as an intermediate nursery habitat that may increase the survivorship of young fish. Mangroves in the Caribbean strongly influence the community structure of fish on neighbouring coral reefs. In addition, the biomass of several commercially important species is more than doubled when adult habitat is connected to mangroves. The largest herbivorous fish in the Atlantic, Scarus guacamaia, has a functional dependency on mangroves and has suffered local extinction after mangrove removal. Current rates of mangrove deforestation are likely to have severe deleterious consequences for the ecosystem function, fisheries productivity and resilience of reefs. Conservation efforts should protect connected corridors of mangroves, seagrass beds and coral reefs.

Preliminary Survey of Fish Community Composition in Seagrass Habitat in Two Back-Reef Lagoons of the Southern Mexican Caribbean

Article

Full-text available

Jan 2008

Little is known about seagrass fish communities in the southern Mexican Caribbean. Diurnal and nocturnal fish community structure in seagrass habitat were compared between back-reef lagoons using a visual census technique in a natural protected area within a national park (Xcalak) and an unprotected area (Mahahual). Seagrass fish communities differed significantly between the two locations in the daytime and Xcalak supported greater total fish densities. Species richness did not differ statistically between locations. Observed nighttime fish communities were characterized by low spe-cies richness and low fish abundance when compared to diurnal communities. Heavy tourist use and coastal development may have degraded seagrass habitat at Mahahual causing lower fish abundance. Also, proximity of seagrass to man-grove habitat in Xcalak may have led to increased abundance and differences in species composition between locations. More extensive analysis and monitoring of the relative functioning of back-reef habitats in these two systems is needed as coastal development and fishing pressure continue to threaten the area. RESUMEN: No se conoce mucho sobre la comunidad de peces en pastos marinos en el sur del Caribe mexicano. La estruc-tura de las comunidades de peces nocturnas y diurnas en pastos marinos se obtuvo mediante censos visuales y se compar6 entre la laguna arrecifial de un area protegida (Parque Nacional Arrecifes de Xcalak) y un area nclprotegida (Mahahual). Las comunidades de peces fueron diferentes significantemente entre 10s dos sitios durante el dia, Xcalak registr6 las mayores densidades de peces. No existe diferencia estadisticamente significativa con respecto a la riqueza de especies entre sitios. Las comunidades de peces nocturnas presentaron valores bajos de riqueza de especies y de abundancia con respecto a las comunidades diurnas. El desarrollo turistico y costero de Mahahual, podrian estar degradando el habitat de pastos marinos, y como consecuencia el registro de baias abundancia de peces. En contraste, en Xcalak, la proximidad del ecosistema de manglar adyacente a 10s pastos marinos podria estar influenciando con una mayor abundancia de peces y cambios en la composition de especies con respecto a Mahahual. Mientras en el area continue el desarrollo costero y la pesca en el area, es necesario un analisis mas extensivo (escala temporal y espacial) del funcionamiento de ambas lagunas arrecifales.

Ontogenetic Patterns in Diet and Feeding Morphology in Sympatric Sparid Fishes from Seagrass Meadows

Article

Full-text available

Feb 1984
COPEIA

The sparids Lagodon rhomboides and Diplodus holbrooki were spatially and temporally sympatric and demonstrated similar growth patterns on seagrass meadows of Apalachee Bay, Florida. Both species took a wide variety of food items over the growth period, but distinctly different trophic stages exist for both fishes and dietary overlap between the species was small. Ontogenetic and interspecific variation in the diets of the fishes was correlated with differences in external morphology related to locomotion, mouth dimensions and ontogeny of dentition. With an elongated body form, large mouth and sharp incisors as a juvenile, Lagodon is a generalized predator dependent upon motile epibenthic invertebrates. Diplodus specializes on hydroids and microepiphytes; this is related to early development of chisel-type incisors, deep-bodied form and small mouth. Consumption of seagrasses as a primary food source was associated with the presence of vertically opposed, straight-edged incisors in Lagodon. Consumption of epiphytes and sponges in adult Diplodus was related to the development of long, rounded and protruding incisors, greater numbers of posterior teeth and strong jaws. This study provides support for the hypothesis that ontogenetic and interspecific differences in the diets of fishes are related to morphological characteristics and affirms the usefulness of the "ontogenetic trophic unit" concept.

Landscape-scale variation in forest structure and biomass in a tropical rain forest. For Ecol Manage

Article

Full-text available

Oct 2000
FOREST ECOL MANAG

A better understanding of the reasons for variation in tropical rain forest (TRF) structure is important for quantifying global above-ground biomass (AGBM). We used three data sets to estimate stem number, basal area, and AGBM over a 600-ha old-growth TRF landscape (La Selva, N.E. Costa Rica). We analyzed the effects of soil type, slope angle, topographic position, and different sample designs and measurement techniques on these estimates. All three data sets were for woody stems ≥10 cm in diameter. Estimated AGBM was determined from stand-level measurements using Brown’s (Brown, 1997) allometric equation for Tropical Wet Forest trees. One data set was from three subjectively-sited 4-ha plots (the ‘OTS plots’), another was based on 1170 0.01 ha plots spaced on a regular grid (the ‘Vegetation map plots’), and the third was from 18 0.5 ha plots (the ‘Carbono plots’) sited to provide unbiased samples of three edaphic conditions: flat inceptisol old alluvial terraces; flat ultisol hill-tops; and steep ultisol slopes. Basal area, estimated AGBM and the contributions of major life forms were similar among studies, in spite of the differences in sampling design and measurement techniques. Although the Carbono plots on flat inceptisols had significantly larger and fewer trees than those on ultisols, AGBM did not vary over the relatively small edaphic gradient in upland areas at La Selva. On residual soils, the largest trees were on the flattest topographic positions. Slope angle per se was not correlated with basal area or AGBM within the residual soils. Errors introduced by palm and liana life forms, as well as hollow trees, did not significantly affect AGBM estimates. In contrast, the methods used to measure buttressed trees had a large impact. Plot sizes of 0.35–0.5 ha were sufficient to achieve coefficients of variation of <12% for basal area with only six replicates in a given edaphic type. AGBM estimates ranged from 161 to 186 Mg/ha. These low values appear to be mainly due to the Tropical Wet Forest allometry equation used. This in turn may be indicative of a real and substantially lower ratio of biomass/basal area in Tropical Wet Forest than in Tropical Moist, as previously noted by Brown (1996).Our results indicate that for upland TRF landscapes with levels of environmental variation similar to La Selva, AGBM will be relatively insensitive to soil type and topography. However, because topography and soil type had much stronger effects on stem size, stand density, and spatial heterogeneity of stems, stand dynamics may be more sensitive than AGBM to this range of conditions. We recommend that future studies of landscape-scale forest structure employ stratified sampling designs across major environmental gradients. Unbiased sampling with replication, combined with consistent and well-documented measurement techniques, will lead to a greatly improved understanding of the magnitude of and reasons for variation in forest structure and AGBM within TRF landscapes.

Movement of gray snapper Lutjanus griseus among subtropical seagrass, mangrove, and coral reef habitats

Article

Full-text available

Apr 2009

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

Shallow-water refuge paradigm: Conflicting evidence from tethering experiments in a tropical estuary

Article

Full-text available

Nov 2007

The shallow-water refuge paradigm has been globally applied to help explain the high abundances of juvenile fishes that utilise shallow-water estuarine nursery habitats. Despite the wide application and acceptance of the paradigm, there is little direct evidence to indicate that small juvenile fishes benefit from reduced predation pressure in shallow water habitats relative to adjacent deeper waters. The present study employed chronographic tethering experiments to examine patterns in predation potential across a depth gradient (0.2 to 3 m) in the lower reaches of a tropical estuary in northeastern Queensland, Australia. Over 6 mo, 17 replicate experimental trials were conducted, deploying a total of 183 tethered fish prey. Despite the clear and consistent patterns found in the few previous studies elsewhere in the world, there was no significant effect of depth on predation pressure, and thus no evidence of lower predation pressure in the shallow relative to the adjacent deeper estuarine waters examined in the present study. The findings suggest that the shallow-water refuge paradigm may be too simplistic for diverse and complex tropical estuarine nursery grounds.

Marine nurseries and effective juvenile habitats: Concepts and applications

Article

Full-text available

Apr 2006
MAR ECOL-PROG SER

Much recent attention has been focused on juvenile fish and invertebrate habitat use, particularly defining and identifying marine nurseries. The most significant advancement in this area has been the development of a standardized framework for assessing the relative importance of juvenile habitats and classifying the most productive as nurseries. Within this framework, a marine nursery is defined as a juvenile habitat for a particular species that contributes a greater than average number of individuals to the adult population on a per-unit-area basis, as compared to other habitats used by juveniles. While the nursery definition and framework provides a powerful approach to identifying habitats for conservation and restoration efforts, it can omit habitats that have a small per-unit-area contribution to adult populations, but may be essential for sustaining adult populations. Here we build on the nursery concept by developing a framework for evaluating juvenile habitats based on their overall contribution to adult populations, and introduce the concept of Effective Juvenile Habitat (EJH) to refer to habitats that make a greater than average overall contribution to adult populations.

Nature and consequences of biological connectivity in mangrove systems

Article

Full-text available

Nov 2005

Marcus Sheaves

Mangroves are important nursery and feeding areas for fish. Their rich invertebrate faunas render them productive feeding areas, while their shallow waters and structural complexity provide sanctuary habitats at a variety of scales. However, in most parts of the world mangroves are available to fish for only part of the time because they are alternately inundated and exposed by the high-tide/low-tide cycle. As a result, few fish can use mangroves exclusively but must migrate in and out of the mangroves with the tide, occupying alternative habitats when mangroves are unavailable. These movements connect the mangroves and the alternative habitats to form an 'interconnected habitat mosaic'. Living in a habitat mosaic puts limits on the patterns of life possible in mangrove systems, complicates trophic structures, and creates the need for tactics and strategies to meet the challenges imposed by movement among components of the mosaic. Moreover, this biological connectivity means that understandings of trophic relationships, life-history strategies, predation and mortality, and patterns of distribution and abundance must be set in a spatially and temporally variable context. Despite the obvious consequences and importance of biological connectivity in mangrove ecosystems, it has often not been given appropriate consideration in the development of theories and paradigms.

Are Caribbean mangroves important feeding grounds for juvenile reef fish from adjacent seagrass beds?

Article

Full-text available

Jun 2004

Little evidence is available on how juvenile fishes utilise seagrass beds and adjacent mangroves as feeding habitats. In this study we tested the degree to which Caribbean mangroves are utilised as feeding grounds by the fish community from adjacent seagrass beds. Stable carbon and nitrogen isotope analyses were performed on several potential food items from seagrass beds and adjacent mangroves, on muscle tissue of 23 fish species from seagrass beds on a Caribbean island (Curacao, Netherlands Antilles), and on juveniles of 2 common reef fish species, Haemulon flavolineatum and Ocyurus chrysurus, from seagrass beds in 7 bays on 5 Caribbean islands. Only the herbivore Acanthurus chirurgus and the carnivore Haemulon chrysargyreum appeared to feed predominantly in the mangrove habitat, whereas the carnivores Mulloidichthys martinicus and O. chrysurus (only on 2 islands) showed a stable carbon signature suggestive of food intake from the mangrove as well as the seagrass habitat. The piscivore Sphyraena barracuda foraged on fish schooling at the mangrove/seagrass interface. For the other 18 seagrass fish species, which contributed 86 % of the total seagrass fish density, the contribution of food sources from the mangroves was minor to negligible. The same was true for H, flavolineatum and 0, chrysurus on most of the other Caribbean islands. The results contrast with the situation in the Indo-Pacific, where intertidal mangroves serve as important feeding habitats for fishes from adjacent systems during high tide. This difference is most probably explained by both the absence of large tidal differences on Caribbean islands and the greater food abundance in seagrass beds than in mangroves.

Dependence of Caribbean reef fishes on mangroves and seagrass beds as nursery habitats: A comparison of fish faunas between bays with and without mangroves/seagrass beds

Article

Full-text available

Apr 2001

Mangroves and seagrass beds are considered important nursery habitats for coral reef fish species in the Caribbean, but it is not known to what degree the fish depend on these habitats. The fish fauna of 11 different inland bays of the Caribbean island of Curacao were compared; the bays contain 4 different habitat types: seagrass beds in bays containing mangroves, seagrass beds in bays lacking mangroves, mud flats in bays containing mangroves and seagrass beds, and mud flats in bays completely lacking mangroves and seagrass beds. Principal component analysis showed a high similarity of fish fauna among bays belonging to each of the 4 habitat types, despite some differences in habitat variables and human influence between bays. Juveniles of nursery species-fish species using mangroves and seagrass beds as juvenile nurseries before taking up residence on reefs-showed highest abundance and species richness on the seagrass beds, and on the mud flats near mangroves and seagrass beds, but were almost absent from bays containing only mud flats. The high abundance and species richness on the mud flats near nursery habitats can be explained by fishes migrating from the adjacent mangroves/seagrass beds to the mud flats. Seagrass beds near to mangroves showed a higher richness of nursery species than did seagrass beds alone, suggesting an interaction with the mangroves resulting in an enhancement of species richness. Comparison of fish densities from the 4 different habitat types indicates that for the nursery species the degree of dependence on a combination of mangroves and seagrass beds as nurseries for juvenile fish is high for Ocyurus chrysurus and Scarus iserti, the dependence on seagrass beds is high for Haemulon parrai, H, sciurus, Lutjanus apodus, L, griseus, Sparisoma chrysopterum and Sphyraena barracuda, and the dependence on mud flats near mangroves/seagrass beds is high for L. analis. The dependence on mangroves and/or seagrass beds is low for Chaetodon capistratus, Gerres cinereus, H, flavolineatum and L. mahogoni, which can also use alternative nursery habitats.

Tethering experiments and hypothesis testing in ecology

Article

Full-text available

Jan 1995

Segregation along multiple resource axes in a tropical seagrass fish community

Article

Full-text available

Feb 2006

Segregation of resources is supposed to be a mechanism for coexistence of species and/or life stages when resources are limiting and competition between species occurs. In seagrass beds, fish species richness is lower than on coral reefs, but food abundance is in general higher. In this case, food segregation may not occur. Here, the null hypothesis is tested that species show no segregation in feeding with respect to time, space and diet. The structure of the food web in a tropical seagrass bed revealed that the seagrass fish community consisted of species feeding at 3 trophic levels: (1) herbivores, (2) omnivores, zoobenthivores and zooplanktivores, and (3) piscivores. The data suggest that herbivores partitioned food by specialising on seagrass epiphytes, seagrass leaves or macroalgae from the seagrass bed, with 1 species presumably feeding in adjacent mangroves. Fishes at the second trophic level showed temporal segregation in feeding habits between fish families, while species within families showed segregation in food type and source. At the third trophic level, 1 piscivorous species was found. The majority of fish species showed a very narrow diet breadth with a significant segregation in resource-use. The null hypothesis was rejected since feeding segregation was not random for time, space and diet, viz. feeding time and diet (33.3%), diet only (25.5%), time, habitat and diet (15.2%), habitat and diet (13.4%), time only (3.5%) and habitat only (2.6%). Segregation in resource use was present along 1 to 3 resource axes simultaneously, which could support coexistence of species that favour comparable food types if food were limiting.

Mangrove habitats as nurseries: unique assemblages of juvenile fish in subtropical mangroves in eastern Australia

Article

Full-text available

Oct 1995

A total of 53 species of juvenile fish were caught over a 2 yr study period in 2 mangrove lined estuaries in Moreton Bay, eastern subtropical Australia. Comparing juvenile fish communities among mangrove forests, seagrass beds and mudflats identified significant differences in species richness and abundances of juveniles. Seagrass communities comprised distinct species of resident and nonresident fish species of little economic importance. Mangrove forests and mudflats had many shared species (but mangrove forests were dominated by smaller or younger juveniles in greater abundances; Laegdsgaard unpubl. data). Mudflat habitats appear to be transition zones between juvenile and adult habitats. Only 4 species were exclusive to seagrass whereas 27 species were exclusive to the mangrove/mudflat habitat. Juveniles of 7 of the 10 commercially harvested fish species in Moreton Bay were found in greatest numbers in mangrove forests. Salinity, temperature and turbidity were similar in all habitats so could not account for differences in habitat choice of juvenile fish. Most juvenile fish in mangroves during summer were nonresidents and species richness and abundance were highest in summer and lowest in winter. There were significant differences among sites and years in the numbers of species and individuals; however, the trends were similar and demonstrated clearly that mangrove sites within Moreton Bay play a more important role and have greater potential as nursery habitats than do adjacent habitats. Preferential selection of mangrove habitats by juvenile fish, particularly commercial species, indicates a need for conservation.

Relative importance of interlinked mangroves and seagrass beds as feeding habitats for juvenile reef fish on a Caribbean island

Article

Full-text available

Jun 2004

Mangroves and seagrass beds are important daytime shelter habitats for juvenile Caribbean reef fish species, but little is known about their relative importance as feeding grounds. In the present study, we tested the degree to which these 2 habitats are used as a feeding ground for 4 nocturnally active fish species on Curacao, Netherlands Antilles. Stable isotope analysis was used as a technique to distinguish between feeding in mangroves and seagrass beds. Individuals of the 4 species which were sheltering during the daytime in permanently inundated fringing mangroves subject to low tidal exchange showed a stable carbon isotope signature indicative of a mixed diet composed of crustaceans from mangroves as well as seagrass beds, with the contribution from mangrove food items lying between 57 and 92%. However, individuals of the same species sheltering on adjacent (

Selective use of mangrove shorelines by snappers, grunts, and great barracuda

Article

Full-text available

Mar 2008
MAR ECOL-PROG SER

We examined seasonal utilization of >500 km of mangrove shoreline within a subtropi- cal continental system by Lutjanus griseus, L. apodus, Haemulon sciurus, H. parra, and Sphyraena barracuda over 2 consecutive years. Mangrove use by these species was examined in terms of fre- quency of occurrence, density (fish 60 m-2), concentration (density among samples where number of fish ≥1), and selection (H0: habitat use = availability). All species exhibited either seasonal or spatial habitat selection. Mangrove shorelines closest to the reef tract (Keys) were used by snappers and grunts at much greater levels than their availability would suggest, whereas more inland and expan- sive mangrove shorelines were largely selected against. This selection pattern was evident year round for L. apodus, H. sciurus, and H. parra. In contrast, L. griseus preferred more inland mangroves during the dry season and Keys mangroves during the wet seasons. S. barracuda exhibited selection for Keys during the wet seasons and was the only species to exhibit non-selection (random) patterns among strata during the dry seasons. These results demonstrate that mangrove shorelines across broad spatial scales are not equivalent in their value as fish habitats, and that estimates of 'essential fish habitat' or 'nursery habitat' using total habitat area will grossly overestimate the amount of functional habitat used by these reef fishes.

Mangroves as fish habitat: 50 Years of field studies

Article

Full-text available

Aug 2006
MAR ECOL-PROG SER

Mangroves dominate undisturbed natural shorelines of many sub-tropical and tropical regions, yet their utilization by fishes is poorly understood. To provide the first comprehensive list of empirical field studies for comparative and reference purposes, we assembled and quantified aspects of 111 mangrove-fish surveys published between 1955 and 2005. Differences in the location, purpose, methodology, data gathered, and analyses performed among studies have resulted in a fragmented literature making cross-study comparisons difficult, at best. Although the number of published studies has increased over time, a geographical bias in the literature has persisted towards studies performed in the USA and Australia, and against studies performed in Southeast Asia and West Africa. The typical survey design has examined <10 fixed locations on a monthly or bimonthly basis for a period of less than 2 yr. Water temperature and salinity measurements have been the most reported habitat variables; others, such as structural and landscape measures, continue to be rare. Moreover, the focus to date has been on identifying assemblage-level patterns of fish use, with very few studies providing species-specific estimates of abundance, growth, mortality, and secondary production. Unless future studies strive towards obtaining such estimates, gauging the importance of mangroves as fish habitat and their broader contribution to ecosystem diversity and production will remain elusive.

Spatial and temporal variations in mangrove and seagrass faunal communities at Bimini, Bahamas

Article

Full-text available

May 2007
B MAR SCI

Mangrove and nearshore seagrass macrofaunal communities were concurrently sampled in two areas of contrasting primary productivity (North Sound: low; South Bimini: high) off Bimini, Bahamas. Over 200,000 individuals, comprising 175 species, were identified from catches of block nets, seines, and trawls between March 2000 and March 2003. The Index of Relative Importance (IRI), which is typically used for dietary analysis and combines percentage weight, abundance and occurrence, was applied to catch data to enable easy spatial and temporal variations in community composition. Cluster-analysis revealed distinct mangrove and seagrass communities, with Morisita's index indicating a greater degree of spatial and temporal homogeneity in the North Sound. Catch diversity and biomass were significantly greater in the mangroves than over seagrass in both locations, and highest off South Bimini. Low productivity, faunal diversity, and abundance in the North Sound were probably due to extreme abiotic variables. Juveniles of most species were present in mangroves and seagrass beds around Bimini, and therefore the protection of mangroves in the Bahamas should be an issue of immediate concern.

Nearshore habitat use by gray snapper (Lutjanus griseus) and bluestriped grunt (Haemulon sciurus): environmental gradients and ontogenetic shifts

Article

Full-text available

May 2007
B MAR SCI

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.

Species-specific patterns of fish abundance and size along a subtropical mangrove shoreline: An application of the delta approach

Article

Full-text available

May 2007
B MAR SCI

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.

Trophic Linkages Among Primary Producers and Consumers in Fringing Mangroves of Subtropical Lagoons

Article

Full-text available

Mar 2004
B MAR SCI

Fringe mangroves associated with islands of the subtropical Atlantic/Caribbean region create extensive subtidal mangrove epibiont communities. While increasingly recognized as an important habitat, few studies have focused on the trophic structure of communities associated with mangrove prop-roots. We examined trophic linkages among primary producers (mangroves, seagrass, and algae) and consumers using stable carbon and nitrogen isotopes in fringe mangroves of the Bahamas and Biscayne Bay, Florida. The average 13C value of primary consumers (16.4) was similar to macroalgae (16.7) and seagrass epiphytes (14.6) and highly distinguishable from mangroves (27.4). Higher secondary consumers had enriched 13C values (10.1) relative to primary consumers, and were similar to average seagrass 13C values (10.5). The ranges of 15 N signatures of vertebrate (6.312) and invertebrate (0.410.7) consumers indicated a multi-trophic structure. Based on mixing equations, the majority of primary consumers diet was algal based, while secondary consumers depended on both algal and seagrass carbon. Mangroves do not appear to be the major source of carbon to consumers in fringe mangroves of subtropical lagoons. Rather, fringe island-associated mangroves constitute refugia for invertebrates and young reef fishes, and create substrate for a diversity of primary producers and consumers, thereby playing an important indirect role to the food web of these systems.

Habitat fragmentation affects fish secondary production in Bahamian tidal creeks

Article

Full-text available

May 2007
B MAR SCI

We provide an example of how fish secondary production can be used to assess effects of anthropogenic stress on ecosystem function. Specifically, we demonstrate that fragmentation of hydrologic connectivity in small tidal creeks on Andros Island, Bahamas, decreases secondary production by as much as an order of magnitude for five economically important fish species: gray snapper (Lutjanus griseus Linnaeus, 1758), schoolmaster snapper (Lutjanus apodus (Walbaum, 1792)), cubera snapper (Lutjanus apodus cyanopterus (Cuvier, 1828)), blue striped grunt (Haemulon sciurus (Shaw, 1803)), and sailor's choice (Haemulon parra (desmarest, 1823)). We conducted more than 800 individual quadrat surveys, in eight creeks that varied in degree of habitat fragmentation, to estimate total biomass for the focal species. Biomass values were multiplied by in situ or published growth rates to calculate annual secondary production. Differences in estimates of secondary production among creeks were attributable to fewer species, fewer individuals, and smaller individuals in fragmented creeks. Secondary production estimates are a useful way to measure responses of ecosystem function to anthropogenic stress because they are a composite value that incorporates many important aspects of ecosystem function.

Mangrove shoreline fishes of Biscayne Bay, Florida

Article

Full-text available

Jan 2003
B MAR SCI

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.

The Identification, Conservation, and Management of Estuarine and Marine Nurseries for Fish and Invertebrates

Article

Full-text available

Sep 2009

Michael W. Beck, Kenneth L. Heck, Jr., Kenneth W. Able, Daniel L. Childers, David B. Eggleston, Bronwyn M. Gillanders, Benjamin Halpern, Cynthia G. Hays, Kaho Hoshino, Thomas J. Minello, Robert J. Orth, Peter F. Sheridan and Michael P. Weinstein

High connectivity of Indo-Pacific seagrass fish assemblages with mangrove and coral reef habitats

Article

Full-text available

Jan 2008

Marine ecosystems throughout the Indo-Pacific region are highly threatened by anthropogenic stressors, yet the faunal interaction between different component habitats remains poorly understood. This information is vital as stress on one inter-connected habitat may have cascade effects on other habitats. The present study focused on the impact of inter-habitat connectivity on seagrass fish assemblages, specifically between seagrass, mangrove and reef habitats. Fish were sampled using a seine net within 3 seagrass habitats (seagrass near to reef, seagrass near to reef and mangrove, and seagrass near to mangrove) within eastern Indonesia. Visual surveys were also conducted within mangrove habitats. Fish abundance and species richness in seagrass beds in close proximity to mangroves was at least twice that found in seagrass beds that were distant from mangrove habitat. The trophic structures of seagrass fish assemblages change from being dominated by predators and omnivores close to the reef, to assemblages high in planktivores and herbivores close to mangroves. We found that mangroves enhance the fish assemblages of nearby seagrass beds probably by increasing the availability of shelter and food provision. This study indicates that Indo-Pacific seagrass beds play an important fish nursery role, which is influenced by the availability of nearby reef and mangrove habitats. Our research supports the need for ecosystem-level management of shallow water tropical habitats, but also suggests that successful management requires local-level knowledge of habitat interactions to successfully enhance or conserve fish assemblages

Fish assemblages in seagrass beds are influenced by the proximity of mangrove forests

Article

Full-text available

Feb 2007

Mangrove forests and seagrass beds frequently occur as adjacent habitats in the temperate waters of southeastern Australia. At low tide when fish cannot occupy mangroves they might utilise adjacent habitats, including seagrass. We first sampled small fish from seagrass beds close to and far from mangroves in the Pittwater estuary, NSW, Australia. Seagrass beds close to mangroves had a greater density of fish species than beds far from mangroves (close: mean 16.0speciesnet−1, SE 1.0; far: 13.2, 1.3; P<0.05). In particular, juvenile fish were in greater densities near to than far from mangroves (close: 5.3, 0.4; far: 3.1, 0.4; P<0.05). We then sampled the mangrove forests during the high tide and seagrass beds during the low tide, in beds along a continuum of distances from mangroves. Multivariate analysis showed that fish assemblages differed with distance from mangroves, and the differences were attributed to the composition of the fish assemblage (i.e. presence/absence of fish species), not the abundances of individual species. In particular, fish that utilise mangrove forests at high tide were found in greater species densities and species richness in seagrass nearer to mangroves. A negative relationship was found between the density of mangrove-utilising fish species and the distance of the bed from mangroves (R 2=0.37, P<0.05). This confirms the important connectivity between mangroves and seagrass for fish in temperate Australian waters.

The value of patches of intertidal seagrass to prawns depends on their proximity to mangroves

Article

Full-text available

Jun 2005

Penaeid prawns were sampled with a small seine net to test whether catches of postlarvae and juveniles in seagrass were affected by the distance of the seagrass (mainly Zostera capricorni) from mangroves and the density of the seagrass in a subtropical marine embayment. Sampling was replicated on the western and eastern sides of Moreton Bay, Queensland, Australia. Information on catches was combined with broad-scale spatial information on the distribution of habitats to estimate the contribution of four different categories of habitat (proximal dense seagrass, distal dense seagrass, proximal sparse seagrass, distal sparse seagrass) to the overall population of small prawns in these regions of Moreton Bay. The abundance of Penaeus plebejus and Metapenaeus bennettae was significantly and consistently greater in dense seagrass proximal to mangroves than in other types of habitat. Additionally, sparse seagrass close to mangroves supported more of these species than dense seagrass farther away, indicating that the role of spatial arrangement of habitats was more important than the effects of structural complexity alone. In contrast, the abundance of P. esculentus tended to be greatest in sparse seagrass distal from mangroves compared with the other habitats. The scaling up of the results from different seagrass types suggests that proximal seagrass beds on both sides of Moreton Bay provide by far the greatest contribution of juvenile M. bennettae and P. plebejus to the overall populations in the Bay.

The behavior of heterotypic resting schools of juvenile grunts (Pomadasyidae)

Article

Full-text available

Aug 1977

Resting schools of juvenile grunts (less than 12 cm length), composed primarily of Haemulon flavolineatum and H. plumieri, were studied from 1972 to 1976 on a series of patch reefs surrounded by seagrass beds on the northeast coast of St. Croix, U.S. Virgin Islands. Juvenile grunts form large inactive multispecies schools in reef areas by day. Repeated censuses over several years reveal that certain parts of the reef, particularly those with large formations of the corals Porites porites and Acropora palmata, are traditional schooling areas. When the fishes reach a size of about 15 cm, the H. plumieri form homotypic schools which roam the patch reefs but are no longer associated with particular formations of coral. In contrast, larger H. flavolineatum are uncommon on the patch reefs and they may move offshore to deeper water. The schools of juvenile grunts migrate some distance away (often 100 to 300 m) into seagrass-covered areas to feed on invertebrates at dusk each day. The routes which are followed into the seagrass beds are precise and persist over years. At dawn the grunts return to the reef on the same routes. Mass marking and release experiments show that juvenile grunts will move over long distances (approximately 3 km) to reach a home reef.

Modelling skewed data with many zeros: A simple approach combining ordinary and logistic regression

Article

Full-text available

Mar 2005

We discuss a method for analyzing data that are positively skewed and contain a substantial proportion of zeros. Such data commonly arise in ecological applications, when the focus is on the abundance of a species. The form of the distribution is then due to the patchy nature of the environment and/or the inherent heterogeneity of the species. The method can be used whenever we wish to model the data as a response variable in terms of one or more explanatory variables. The analysis consists of three stages. The first involves creating two sets of data from the original: one shows whether or not the species is present; the other indicates the logarithm of the abundance when it is present. These are referred to as the presence data and the log-abundance data, respectively. The second stage involves modelling the presence data using logistic regression, and separately modelling the log-abundance data using ordinary regression. Finally, the third stage involves combining the two models in order to estimate the expected abundance for a specific set of values of the explanatory variables. A common approach to analyzing this sort of data is to use a ln (y+c) transformation, where c is some constant (usually one). The method we use here avoids the need for an arbitrary choice of the value of c, and allows the modelling to be carried out in a natural and straightforward manner, using well-known regression techniques. The approach we put forward is not original, having been used in both conservation biology and fisheries. Our objectives in this paper are to (a) promote the application of this approach in a wide range of settings and (b) suggest that parametric bootstrapping be used to provide confidence limits for the estimate of expected abundance.

Investigations on the Gray Snapper, Lutjanus griseus

Article

Dec 1971
COPEIA

Statistical Principles of Experimental Design

Article

Jan 1962

B.J. Winer

First International symposium on mangroves as fish habitat - Preface

Article

May 2007
B MAR SCI

Systematics and life history of the great barracuda Sphyraena barracuda (Walbaum)

Article

Jan 1963

D.P. De Sylva

Recruitment and Essential Habitat of Juvenile Sand Seatrout (Cynoscion arenarius) in Four Estuaries Along the West Coast of Florida

Article

Jun 2007

The sand seatrout (Cynoscion arenarius) is an ecologically and economically important species common to estuarine and nearshore waters of the Gulf of Mexico. Currently, comprehensive information on the essential habitat of juvenile sand seatrout is limited. We analyzed data from a long-term fisheries-independent monitoring program to assess the spatial and temporal distributions of juvenile sand seatrout relative to various habitat parameters in four estuaries (Apalachicola Bay, the Suwannee River estuary, Tampa Bay, and Charlotte Harbor) along the gulf coast of Florida. A total of 25,668 sand seatrout (≤5 100 mm SL) were collected during monthly stratified-randozo sampling from Jan. 1996 through Dec. 1997 and Jan. 2001 through Dec. 2003. Specimens were collected with 21.3-m bag seines and 6.1-m otter trawls; the majority of specimens were captured in trawls from water ≥ 1.8 in deep. Juvenile sand seatrout primarily recruited into the estuaries from May through Oct., although recruitment began 1 mo earlier in Tampa Bay. Juveniles were most abundant over unvegetated mud bottoms, in mesohaline salinities, and near salt marsh vegetation. Highest abundances also occurred in small rivers, tidal creeks, and areas adjacent to the mouths of large rivers. Juveniles between 30 mm SL and 70 mm SL primarily occupied mesohaline salinities before shifting toward higher salinities as they approached 100 mm SL.

Night habits of fishes of Alligator Reef, Florida

Article

Jan 1966

Recruitment of Coral Reef Fishes: Effects of Distribution of Predators and Shelter

Article

Jun 1985

Myra Shulman

Factors affecting recruitment and early survivorship of juvenile coral reef fishes were studied on St Croix, US Virgin Islands. The faunal assemblage studied included diurnally active fishes found in the rubble/sand habitat. The most abundant members were: beaugregory Stegastes leucostictus, foureye butterflyfish Chaetodon capistratus, mahogany snapper Lutjanus mahogoni, surgeonfishes Acanthurus bahianus and A. chirurgus, and French grunt Haemulon flavolineatum. Recruitment of juveniles of almost all species in the rubble/sand fish assemblage occurred more heavily on reefs that were built 20-40 m away from the main reef (into the lagoon) than on those built at the edge of the backreef, probably due to differences in available shelter and differences in encounter rates with predators. Seagrass and algae, which provide shelter to very small juvenile fishes, are absent in a 'halo' zone close to the reef due to the feeding activities of reef-associated grazers (fishes and urchins). Part of the explanation for the observed spatial pattern of fish recruitment is the spatial pattern of the shelter provided by seagrass and algae. Risk of predation for small juvenile fishes was considerably higher close to the reef than it was 20 m away. -from Author

Plankton, epibenthos and fish communities

Chapter

Jan 1992

Diurnal-Nocturnal Activity of Some Inshore Fishes in the Gulf of California

Article

Sep 1965
COPEIA

Edmund S. Hobson

Diurnal and nocturnal habits of some inshore fishes were observed in the southern Gulf of California. Certain patterns of behavior within and between species were consistently observed, and permit a number of tentative generalizations regarding feeding habits, schooling, and other activity in relation to time of day. Species with predominently diurnal foraging habits include: Mycteroperca rosacea (Streets), Epinephelus labriformis (Jenyns), Chromis atrilobata (Gill), Eupomacentrus rectifraenum (Gill), Abudefduf troschelii (Gill), Bodianus diplotaenia (Gill), Thalassoma lucasanum (Gill), Scarus californiensis (Pellegrin), Heniochus nigrirostris (Gill), Prionurus punctatus Gill, Runula azalea Jordan and Bollman, Balistes verres Gilbert and Starks, and Balistes polylepis Steindachner. Species obtaining most of their food at night include: Holocentrus suborbitalis (Gill), Myripristis occidentalis Gill, Rypticus bicolor (Valenciennes), Lutjanus argentiventris (Peters), Apogon retrosella (Gill), Microlepidotus inornatus Gill, Anisotremus interruptus Gill, Haemulon sexfasciatum Gill, Selar crumenophthalmus (Bloch), and Pareques viola (Gilbert). A number of other species are introduced as their activity relates to the discussion. The nocturnal species are predators, while the herbivorous and omnivorous fishes show predominantly diurnal feeding habits. Those species schooling in dense, relatively inactive schools inshore during the day are nocturnal feeders and the school functions in defense against diurnal predators. Members of these schools disperse to feed at night, often after moving a considerable distance offshore.

Grazing halos and predation on juvenile Caribbean surgeonfishes

Article

Aug 1994

H Sweatman

In the Caribbean, recruitment of a number of fishes has been found to be low at the edges of patch reefs, intermediate in the grazed halo and highest in dense seagrass. This has been attributed in part to the activities of reef-based predators. We presented small surgeonfishes held in clear glass bottles at 4 distances up to 20 m from the edges of reefs and found that the rate of encounters with predators (and aggressive territorial herbivores) was high at the reef edges, but encounter rates in the halo were much lower and similar to those in the dense seagrass. The low rate of interactions even 2 m from the reef edge implies that reef-based predators avoid the halo also, presumably because of the risk to themselves of predation from still larger piscivores. This implies that the pattern of recruitment is due to avoidance by recruits rather than the depredations of reef-based predators. Many surgeonfishes recruiting to experimental structures in the seagrass were migrant juveniles rather than settling larvae and we suggest that the gradient in recruitment of surgeonfishes reflects proximity to preferred post-settlement habitats.

Fish communities of interacting shallow-water habitats in tropical oceanic regions

Article

Dec 1989

JD Parrish

Utilization of the red mangrove prop root habitat by fishes in south Florida

Article

Jan 1987

The inherent difficulty of sampling the red mangrove prop root habitat has impeded our understanding of the utilization of this habitat by fishes. A block net and rotenone method was developed and used to sample 2 sites in each of 4 regions in Everglades National Park, Florida (USA). At each site a 3 mm mesh net was used to enclose 3 sides of a mangrove stand while an onshore berm formed the fourth side. Samples collected from the mangrove prop root environment were compared with samples collected using a 2-boat otter trawl in the immediately (8 to 10 m) adjacent, fringing seagrass habitat. The density and biomass of fish collected by the 2 gear were greater in the prop root habitat than in the adjacent fringing seagrass areas. There also were consistent differences in species composition between the 2 habitat types across all 4 geographic regions. Analysis of the stomach contents of gray snapper Lutjanus griseus suggested that smaller snapper tend to feed in the prop root habitat while larger snapper may forage out into adjacent areas to feed. The red mangrove prop root habitat is utilized by a wide variety of fish, and greater attention should be given to evaluating its contribution to fish production in south Florida and elsewhere.

Patterns offish and urchin grazing on Caribbean coral reefs: are previous results typical? Ecology

Article

M. E. Hay

Food Habits of Reef Fishes of the West Indies

Article

Nov 1966

J.E. Randall

Food Habits, Length-Weight Relationship and Condition Factor of Young Great Barracuda, Syphraena Barracuda (Walbaum), from Florida Bay, Everglades National Park, Florida

Article

Jan 1989
B MAR SCI

Thomas W. Schmidt

The food habits of the great barracuda, Syphyraena barracuda, were investigated by examining the stomach contents of fish between 36 and 441 mm TL from the shallow grassbeds of Florida Bay, Everglades National Park, Florida. Juvenile barracuda less than 333 mm fed on small epibenthic fish. Goldspotted killifish, Floridichthys carpio, and rainwater killifish, Lucania parva, were the most common dietary items of juvenile S. barracuda. Food habits of juveniles were relatively constant with season and location within the estuary. Larger food organisms were consumed by adult barracuda. The calculated length-weight relationship for 97 barracuda (33-442 mm TL) was log10W = -5.0148 + 2.8663 log10L, and the mean condition factor was 0.497.

Food Habits of the Sea Bream, Archosargus Rhomboidalis (Linnaeus), and Comparative Growth on Plant and Animal Food

Article

Jul 1978
B MAR SCI

Frank A. Vaughan

Food habits and utilization of plant and animal food by an omnivorous, tropical sparid fish, the sea bream (Archosargus rhomboidalis) were studied. Stomach analysis of fish from Biscayne Bay, Florida, showed changes in the proportion of various food items as the fish grew: 4.1-8.0 cm fork length sea bream ate mostly amphipods; larger fish (8.0-10.0 cm) ate filamentous algae; ingestion of coarser algae and vascular plants increased as fish grew. Molluscs formed a significant portion of the diet of fish greater than 20.0 cm. Sea bream fed mostly during daylight.Juvenile sea bream (8.6-13.0 cm FL) were fed shrimp, or one of two filamentous algae, Enteromorpha flexuosa and Polysiphonia subtilissima, at 25°C, for 18 days, to compare their growth on these foods. The fish had a mean weight gain of 7.87% dry weight when fed shrimp; fish fed on Enteromorpha and Polysiphonia experienced losses similar to those of starved controls (−9.48, −24.64, and −21.60% respectively). Sea bream apparently need animal as well as plant food to survive and grow.

Diel, Lunar and Seasonal Changes in a Mangrove Fish Assemblage off Southwestern Puerto Rico

Article

Nov 1991
B MAR SCI

Visual censusing was used to investigate diel, lunar, and seasonal variations in abundance and composition of a fish assemblage inhabiting a mangrove key off the southwest coast of Puerto Rico. Forty-one species were visually identified among the mangrove prop-roots duing designated census periods: 0700, 1200, 1700, 2200. Statistical analysis indicated distinct trends in diurnal, day versus night, and seasonal abundances. Although diurnal variability was evident, the most pronounced feature was nighttime declines in species abundance. All species present during the day showed marked reduction in numbers or complete absence at night. Unlike coral reef habitats, there was no evidence for a diurnal-nocturnal changeover of species assemblages in the mangroves. Low nighttime abundance was partly due to twilight migrational activities. Movements away from the mangrove prop-root habitat at dusk were observed for a variety of fishes, particularly haemulids. Predictable, well ordered migrations were observed for juvenile French grunts (Haernulon flavolineaturn) and sub-adult bluestriped grunts (H. sciurus). Timing, duration, and pre- and post-migratory behaviors differed among species. Seventy-six% of species examined showed significant (P < 0.05) seasonal differences between Oct/Nov 86 (rainy season) and Apr/May 87 (dry season). Lunar periodicity had no obvious effect on species abundance in this mangrove fish assemblage.

Diet shifts of Caribbean grunts (Haemulidae) and snappers (Lutjanidae) and the relation with nursery-to-coral reef migrations

Article

Aug 2003

The spatial size distribution of grunts and snappers have previously indicated the separation of juveniles in nursery habitats from the adults on the coral reef. This implies life cycle migrations from nursery habitats (such as seagrass beds and mangroves) to the coral reef. If diet shifts are related to such migrations, then the diets of these fish must change before or around the fish size at which such migrations take place. A wide size range of juveniles of two grunt species (Haemulon sciurus and Haemulon flavolineatum) and of two snapper species (Lutjanus apodus and Ocyurus chrysurus) were caught in seagrass beds and mangroves, and their gut contents identified and quantified. Regression analysis between fish size and dietary importance of small crustaceans showed a negative relationship in all four species. Positive relations were found for H. sciurus, L. apodus and O. chrysurus between fish length and the dietary importance of decapods, and for L. apodusand O. chrysurus between fish length and prey fish importance. Critical changes in the fish diets with fish size were examined by application of a Canonical Correspondence Analysis (CCA). The CCA yielded three clusters of size-classes of fishes with similar diets, and application of a Mantel test showed that each of these clusters had significantly different diets, and that each cluster diet was significantly specialised. The size at which a fish species ‘switched’ from one cluster to another was compared with size-at-maturity data and with the typical size at which these species migrate from the nursery habitats to the coral reef. H. sciurus and H. flavolineatum may be prompted to migrate from the nursery habitats to coral reef habitats because of dietary changes, or because of the development of the gonads. For L. apodus and O. chrysurus, a dietary changeover forms a more likely explanation for nursery-to-reef migrations than does sexual maturation because these species reach maturity at sizes much larger than the maximum size of individuals found in nursery habitats. Although other factors may theoretically initiate or promote the migration patterns, the results of this study indicate that ontogenetic dietary changes may crucially influence the nursery-to-coral reef migrations of these reef fish species.

Diel differences in the seagrass fish assemblages of a Caribbean island in relation to adjacent habitat types

Article

Jul 2007
AQUAT BOT

The fish fauna of Thalassia testudinum (König) seagrass beds was studied at two sites in the Grand Cul-de-Sac Marin Bay (Guadeloupe, French West Indies). The first seagrass bed was located near a coral reef and the second was near coastal mangroves. Both habitats were sampled during day and night, using a purse-seine and a trap net. A total of 98 species belonging to 36 families were observed. Distance-based redundancy analyses revealed two site-specific assemblages of fishes. Diel assemblage shifts were more pronounced in the seagrass beds near coral reefs than in those near mangroves, due to the existence of nocturnal trophic incursions of coral reef fishes into seagrass beds. First-order carnivores dominated the trophic structure of the fish assemblages during both day and night. At night, Haemulidae, Holocentridae and Apogonidae took the place of Labridae, Chaetodontidae and Mullidae present by day near the reef. This switch did not occur near the coast where the exchanges between seagrass beds and mangrove appear to be less important than with the reef ecosystem. Thus, it appears that the adjacent seascape habitat setting affects the intensity in diel variability of the seagrass bed fish community.

Short and long-term movement and site fidelity of juvenile Haemulidae in back-reef habitats of a Caribbean embayment

Article

Nov 2007

Studies showing that tagged reef fish connect different habitat types are crucial for effective ecosystem management on a seascape-level, but are rare. Therefore we analysed movement of juvenile Haemulon flavolineatum and Haemulon sciurus among seagrass beds, mangroves and fossilised eroded coral shoreline. Fishes were tagged individually with external, short-term bead-tags (both species) or with internal, long-term coded wire tags (H. flavolineatum only). We also tested the hypothesis that in spatially continuous habitat types with many seemingly suitable resting sites, these fishes show high fidelity to only a small number of sites. The linear distribution range of daytime sites was 4–171m for H. flavolineatum and 4–152m for H. sciurus, but in agreement with our hypothesis, externally tagged fishes showed high fidelity to small spatial areas within this range: the percentage of resightings within a 10m radius of the core area of presence (i.e. the site used most intensively) was 69% for bead-tagged H. flavolineatum, and 62% for H. sciurus during the 47-day study-period. Site fidelity was also present over a longer time span: of the 1114 coded wire tagged H. flavolineatum 51 were recaptured and 49 of them were still present at the tagging location after 163–425days at liberty. Median linear movement within a day was small (5m for H. flavolineatum and 8m for H. sciurus), nonetheless, part of the bead-tagged Haemulidae moved from shoreline shelter habitats (mangroves and rocky shoreline) to adjacent seagrass beds (mean±SD distance moved 23±10m) in the afternoon, likely to start feeding there during daylight. When comparing the habitat type occupied during the late afternoon (15:30–17:30h) and morning (8:00–10:30h) on two subsequent days, most movement occurred from seagrass beds back to shoreline habitats (mean distance moved 23±10m), indicating that in the morning these fishes had returned to shelter sites at the shoreline. The current study thus shows existence of connectivity between back-reef habitats through fish movement on a relatively small spatial scale.

Nocturnal foraging habitats of French and Bluestriped Grunts, Haemulon flavolineatum and H. sciurus, at Tobacco Caye, Belize

Article

Apr 1995

Nancy C. Burke

Nocturnal foraging habitats of Haemulon flavolineatum and H. sciurus were investigated in the backreef habitat around Tobacco Caye, Belize. Grunts leave the reef at dusk to forage in the grass beds and sand flats surrounding the reef. The hypothesis that French and bluestriped grunts use separate foraging habitats was examined by following tagged fishes from their diurnal territories or schooling sites to nocturnal foraging grounds. The tag consisted of a small, glowing Cyalume light stick sutured to the dorsal musculature of the fish, next to the first dorsal fin. Surveys of foraging habitats were done to support the tracking study. Large quadrats (225 m2) were set out over the sand flats and grass beds during the day. The numbers of French and bluestriped grunts feeding in each habitat were counted one hour after dark. Foraging French grunts used sand flats, whereas bluestriped grunts usually fed in grass beds. Repeated sightings of two French grunts and one bluestriped grunt in the same individual night-time locations support the hypothesis that nocturnal foraging sites may be used repeatedly by the same individuals.

What attracts juvenile coral reef fish to mangroves: Habitat complexity or shade?

Article

Jan 2004

The value of mangroves for fish species is usually explained in terms of high food abundance or shelter against predators as a result of high turbidity and structural complexity. In a field experiment, artificial mangrove units (AMUs) were designed as open cages, each of which was provided with a different degree of structural complexity and shade. Fish species that were attracted to the AMUs were identified and counted and the effects of shade and structural complexity, as well as the interaction between the two factors, were tested. Diurnal fish showed a preference for the greatest structured complexity and for a moderate increase in shade. Two nocturnal species common in local mangroves as well as seagrass beds showed statistically significant effects: densities of Haemulon sciurus were positively related to both shade and structural complexity, whereas only shade had a significant positive effect on densities of Ocyurus chrysurus. The experiment indicated that the attractiveness of mangrove vegetation for H. sciurus may be influenced by the structural complexity of the habitat as well as by the degree of shade, and that both factors are equally and separately important. Individuals of O. chrysurus that are attracted to mangroves are more likely to be influenced by the presence of shade than by the degree of structural complexity. The data thus indicated that the positive relationship between fish densities in mangrove habitats and the degree of shade and structural complexity, or both, is species-specific.

Nocturnal fish utilization of a subtropical mangrove‐seagrass ecotone

Abstract

No full-text available

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