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Little Fish, Big Impact: Managing a Crucial Link in Ocean Food Webs
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... Fish predators force the menhaden to move near the surface, where they are more easily eaten by piscivorous birds. Ospreys, along with Bald Eagles, feed on menhaden, which are easily captured from the water surface ( Figure 14.7 (Pikitch et al. 2012(Pikitch et al. , 2014(Pikitch et al. , 2018 ...
... It is hard to imagine or justify that the death rate from predators, diseases, and parasites would be constant over a longer time frame and fixed for all ages. The menhaden story illustrates the scientific principle that Everything Is Connected to Everything Else (the First Law of Ecology) and, therefore, single-species management is ill advised (Pikitch et al. 2012). ...
... Similar forage fishery management controversies exist worldwide, where forage species such as anchovy, sardine, and other forage species support large industrial fisheries, and needs for supporting fish, mammal, and bird predators is poorly quantified (Pikitch et al. 2012(Pikitch et al. , 2018Grémillet et al. 2016Grémillet et al. , 2018Hilborn et al. 2017). ...
... Managing fisheries on small pelagic fish (SPF) is challenging because these are highly variable resources due to their short life span and strong dependence on yearly recruitments [8,93,110]. Furthermore, SPF may show long cyclic trends in abundance as a result of environmental and oceanographic factors [1,69] which amplify the risks of overcapacity [40,41]. ...
... Furthermore, SPF may show long cyclic trends in abundance as a result of environmental and oceanographic factors [1,69] which amplify the risks of overcapacity [40,41]. The fluctuations in abundance, coupled with the shoaling behavior of the species, makes them highly vulnerable to fishing, particularly at low stock sizes, increasing the risk of overfishing and depletion [37,77,93,96]. For these reasons, the history of management of these populations shows several examples of collapses [91,94,95], including among others the Peruvian anchoveta [6,87], the Pacific sardine [50,101], and the North Sea herring [32]. ...
... For instance, management of Chilean sardine and anchovy [122] is precautionary by selecting a fishing mortality target corresponding to 60% spawning biomass per recruit; and for the management of the North Sea Sprat the fishing mortality corresponding to the escapement policy is capped by a maximum value to account for the unknown level of recruitment [102]. The adoption of the Ecosystem based approach for the management of fisheries usually leads to more conservative approaches for SPF, with lower fishing targets or higher minimum biomass threshold levels, to reconcile the fishery objectives with the preservation of SPF role as prey and energy transfer from low to high trophic levels in the ecosystem [24,93,112,124]. In addition, the inclusion of economic considerations in the management objectives favors usually more conservative approaches as well [47,48]. ...
A R T I C L E I N F O Keywords: Fishery management Participatory management Harvest control rule Recruitment index Small pelagic fish Anchovy A B S T R A C T This paper summarizes the lessons learnt for the management of small pelagic fish from the case study of managing the international fishery on the Bay of Biscay anchovy. A constant catch regime ended up with a fishery crash and closure (2005-2009) after a series of recruitment failures. Precautionary advices had been disregarded due to their inability to predict the size of the population during the first half of the year when the major fishery takes place. The crash triggered the EU to develop a long-term management plan in 2008. In the absence of a recruitment indicator, biological risk was minimized through a close coupling between assessment, advice and management, changing the management year to start just after the spring surveys on adults. A major improvement arrived in 2014 by the incorporation of an early recruitment indicator from an autumn acoustic survey on juveniles. This allowed additional exploitation of the resource at similar risk levels. Accordingly, TACs are nowadays set after the recruit survey on a management calendar basis. The interactive collaboration between fishers, scientists, and managers allowed inclusion of the stakeholders' preferences for a biomass-based catch bounded harvest strategy suitable for these valuable fisheries. This strategy allows catches between a minimum and maximum TAC level, to account for an economically viable minimum activity when approaching a minimum biomass threshold level, and for the limited market absorption capacity when exceeding an upper biomass threshold level, respectively. Such strategy was adopted by consensus and supposed a successful participatory process in fishery management.
... One of the main community concerns about large-scale fisheries for small pelagic fishes relate to impacts on key predators (e.g., [50,62]). As a result, the ecological roles of sardines and other species on the marine ecosystems of south-eastern Australia have received considerable scientific attention (e.g., [10,25,58]). ...
This paper documents the discovery of a large sardine (Sardinops sagax) resource off Southeastern Australia. We use information from three ichthyoplankton surveys for jack mackerel to apply the Daily Egg Production Method (DEPM) to the Southeastern sardine stock. Mean daily egg production was estimated from survey data. Spawning area was estimated from the surveys and using a habitat suitability model to predict presence/absence of eggs in unsurveyed areas. Spawning biomass was calculated using adult parameters from the adjacent Southern stock. The spawning biomass in the area surveyed was 262,564 t (95% CI 125,670-326-438 t). Habitat modelling using a conservative threshold suggested that the total spawning biomass was 346,388 t (95% CI 143,936-548,840 t). These results suggest this stock has the capacity to sustain an annual catch of several tens of thousands of tonnes, which is considerably larger than the recent catch of < 2500 t. Our findings provide further evidence that opportunities exist to increase Australia's fisheries production. Risks and challenges associated with establishing a new large-scale sardine fishery, including bycatch and ecological impacts, and opposition from conservation groups and recreational fishers are discussed. We also outline the potential socioeconomic and environmental benefits, including the use of marine protein and oil from a sustainable local source with low environmental impacts as an input to the AU$1.3B Tasmanian salmon aquaculture industry. We emphasize the need to adopt a precautionary approach to developing a new fishery and the critical importance of conducting comprehensive surveys to confirm our findings and inform ongoing management.
... Most of the species mentioned above consist of the bulk of fisheries bycatch of the operating fleets in the region; thus, information on their feeding habits and prey selectivity is scarce (Hofling et al., 2000;Corrêa et al., 2005;Martins et al., 2005;Carvalho and Soares, 2006;Muto et al., 2008). However, information on the trophic ecology of small pelagic fish is crucial to understand their role in energy transfer through the food web (Pikitch et al., 2012;Essington et al., 2015). The intermediate trophic position that small pelagic fish hold in the food web of marine ecosystems suggests that they may function as regulators, controlling both the availability of zooplankton and predatory fishes (Rice, 1995;Smith et al., 2011). ...
... However, intrinsic and extrinsic factors, including abiotic factors such as temperature, salinity, pH, dissolved oxygen and density, can influence the population dynamics of small Clupeidae pelagic fish (Peck et al., 2021). In addition, the high variation in the biomass of populations throughout the year, susceptibility to climate change and recruitment are obstacles to the control of sustainable fishing of these species (Pikitch et al., 2012). ...
The aim of the study was to evaluate the influence of changes in seawater salinity on juvenile Brazilian sardine (Sardinella brasiliensis). Through two assays, the LC50 (96 h) and the zootechnical performance (42 days) were determined, respectively. In the first assay, six treatments of salinity 0, 7, 14, 21, 28 and 35 parts per thousand (ppt) with three replicates were established. For this, 100-L cylinder-conical tanks were used, with 30 individuals with 45-day after eclosion (DAE) per unit, without water renewal and feeding. In the groups of salinity 0 and 7 ppt, all fish died on the first day. The LC50 was estimated at salinity 11.13 ppt. The second trial was designed with five treatments (salinity 7, 14, 21, 28 and 35 ppt), with three replicates. Two thousand-L cylindrical-conical tanks were used, with 30 individuals (58 DAE) per unit, with water renewal and feeding until apparent satiation. In the treatment salinity 7 ppt, all fish died by the second day. At salinity 35 ppt, the highest growth rates (2.78 g) and survival (100%) were observed. Salinity 14 ppt had the lowest survival (83%) and growth (1.48 g). We concluded that the juvenile sardines can be adapted to environments with salinity from 14 ppt, with significant losses. However, salinity 35 ppt showed the highest survival and growth rates.
... The overexploitation and decreased stock of large predatory fish worldwide have caused the low trophic levels, that is, herbivorous fish, to be widely targeted by commercial fishing (Gulka et al., 2017). In the marine food web, the higher levels are sometimes affected by the dominance of a single species belonging to one of the intermediate trophic levels, called the wasp-waist control (Pikitch et al., 2012). Such conditions can be worrisome for fish at higher trophic levels. ...
The purpose of this study was to determine the effects of frequent species population fluctuations and the impact of different rates of exploitation on other ecological links in the food web. The mass‐balanced Ecopath model represents the trophic interactions among the 31 defined functional groups in the Kolahi to Dargahan area, with five main species, including Trichiurus lepturus , Saurida tumbil , Nemipterus japonicus , Sillago sihama , and Cynoglossus arel (from April 2018 to April 2019). To investigate the effects of fishing and environmental disturbances, the Ecopath modeling approach combines software for analyzing ecosystem trophic‐level balances with population dynamic models. In the past 5 years, Hormozgan province has caught more than 45% of the benthic fish caught off the northern coasts of the Persian Gulf. From Kolahi to Dargahan, one of the most important fishing grounds in this province's southeast is located. Food web models are used to represent a marine system's current state, assess stock levels, and predict change over time. Over a year, the first five dominant fish in the study area, S. tumbil , S. sihama , C. arel , N. japonicus , and T. lepturus , were biometrically measured, and their population dynamics parameters as well as feeding ecology indices were analyzed. According to the trophic‐level index results, the five most common species studied in this study belonged to the third ( N. Japonicas , S. sihama , and C. arel ) and fourth ( T. lepturus , and S. tumbil ) trophic levels. The key species with the greatest impact on other groups of studied species were identified as S. tumbil and T. lepturus , respectively. The estimated ecosystem indicators were the system operational power (75846.797), the primary production/respiration ratio (0.034), the connectance index (0.159), and the system omnivory index (0.253). A pedigree index (PI) of 0.38 was estimated for the present model. Overexploitation of T. lepturus could disrupt the aquatic food web and adversely affect the long‐term sustainable use of aquatic resources, according to data. As a result, ecosystem‐based fisheries management should be implemented to find a more appropriate solution to sustainable exploitation in the studied habitat, an important fishing area in the Persian Gulf's north.
... Forage fish play a critical role in marine ecosystems by providing a trophic link between plankton and piscivorous fish, mammals, and marine birds [6]. They are crucial to maintaining healthy ecosystems, contribute directly and indirectly to the economic value of global fisheries, and support the conservation and recovery of many coastal marine species at risk [7,8]. Currently in British Columbia, Canada, Pacific Herring (Clupea pallasii), Pacific Sand Lance (Ammodytes personatus; "Sand Lance") and, to a lesser extent, Northern Anchovy (Engraulis mordax) are thought to be the most ecologically important coastal forage fish [9][10][11]. ...
RPAS (Remotely piloted aircraft systems, i.e., drones) present an efficient method for mapping schooling coastal forage fish species that have limited distribution and abundance data. However, RPAS imagery acquisition in marine environments is highly dependent on suitable environmental conditions. Additionally, the size, color and depth of forage fish schools will impact their detectability in RPAS imagery. In this study, we identified optimal and suboptimal coastal environmental conditions through a controlled experiment using a model fish school containing four forage fish-like fishing lures. The school was placed at 0.5 m, 1.0 m, 1.5 m, and 2.0 m depths in a wide range of coastal conditions and then we captured RPAS video imagery. The results from a cluster analysis, principal components, and correlation analysis of RPAS data found that the optimal conditions consisted of moderate sun altitudes (20–40°), glassy seas, low winds (<5 km/h), clear skies (<10% cloud cover), and low turbidity. The environmental conditions identified in this study will provide researchers using RPAS with the best criteria for detecting coastal forage fish schools.
... Forage fish fulfil large economic, environmental, and social roles worldwide; commercial landings of forage fish have been valued at $5.6 billion per year globally, with landings of species supported by forage fish valued at a further $11.3 billion per year (Pikitch et al. 2012). In Canada, Atlantic herring (Clupea harengus) are by far the most economically significant forage species, accounting for roughly 60% of the value of national forage fish landings in 2018 (DFO 2020d). ...
Atlantic herring (Clupea harengus) are economically and ecologically significant but have been in decline in Atlantic Canada due to an uncertain combination of environmental recruitment controls, predation, and fishing (commercial fishery and poorly documented bait removals). Fisheries and Oceans Canada partially closed Atlantic mackerel (Scomber scombrus) and herring fisheries in March 2022 amid controversy and disagreement. Here, we develop a conceptual model for natural and anthropogenic controls on herring abundance centered on the southern Gulf of St. Lawrence (sGSL) and evaluate the likely importance of each. We provide the first estimates of the magnitude of bait fishery withdrawals in the sGSL. The decline in sGSL herring is likely driven by natural predation exacerbated by fishing. Bait fishery removals were 182 tonnes in 2021, suggesting that previous estimates for removals of spring-spawning herring were ~30% too low. Fisheries closure is consistent with a precautionary approach given uncertainties and irreversibility of stock collapse. Ecosystemic models are needed but will be difficult to develop given the incomplete understanding of prey substitutability and net effect of interacting environmental processes.
Coastal estuarine ecosystems serve as nursery habitats for many commercially and recreationally important fishes. Biodiversity is a structural indicator and has been used as a metric for conservation and management. In the hypersaline Lower Laguna Madre of Texas, a variety of organisms makes their living in and around the dominant seagrass vegetation. This study provides a general assessment of forage fishes biodiversity collected seasonally with bag seines in two sites: Holly Beach (HB) and South Bay (SB) within the most southern Texas bay system as part of a broader study on fish biology. A total of 15,880 fishes representing 32 species were collected during four quarterly samplings through a year (11,795 from HB and 4,085 from SB). Both sites are interconnected as no fishes similarities difference were found, nonetheless, the sites’ variable characteristics (i.e. basin area, seagrasses coverage, connection to the Gulf of Mexico) resulted in significant greater species richness, relative abundances, and diversity in HB than SB for most of the year, suggesting differences in habitat quality or at the very least variation in the availability of habitat types, which are known to contribute to differences in fish diversity attributes.
Gulf menhaden (Brevoortia patronus) support the largest fishery by yield in the Gulf of Mexico (GoM) and are a key forage species for many marine predators. While menhaden stock assessments indicated that overfishing was not likely to have occurred in the past, concerns have been raised regarding the possible effects of menhaden fishing on their predators. In this study, we used a US Gulfwide Ecopath with Ecosim (EwE) model to explore the predicted effects of increased menhaden harvest on the GoM ecosystem and focused our analyses on Gulf menhaden predators. Key menhaden predators identified included king mackerel (Scomberomorus cavalla), Spanish mackerel (Scomberomorus maculatus), sea trout (Cynoscion spp.), red drum (Sciaenops ocellatus), and pelagic coastal piscivores [e.g., bluefish (Pomatomus saltatrix)]. As expected, these predators exhibited reduced biomass in response to increased Gulf menhaden harvest, with a predicted 11% decrease in predator biomass at simulated fishing levels near historical highs. Our results indicate strong relationships between the effects of menhaden fishing and the predator fishing mortality for king mackerel and intermediate relationships for Spanish mackerel, blacktip shark (Carcharhinus limbatus), red drum, large coastal sharks, and pelagic coastal piscivores. Biomass of predator groups such as demersal coastal invertebrate feeders [e.g., drums and croakers (Sciaenidae)] are more affected by menhaden harvest (through trophodynamics interactions and bycatch removal) compared to the isolated effect of their fishing mortality. For almost all the groups examined in the trade-off analysis, with the exception of sea trout, current biomass (2016) was higher than their target biomass representing 75% of their biomass at maximum sustainable yield. In comparison to the time series of fishing mortality rates estimated by the most recent Gulf menhaden stock assessment, the mean ecological reference point (ERP) of 0.862 was exceeded in all but 1 year from 1977 to 2007; however, neither the target nor threshold upper ERP value has been exceeded since 2008. The observed Gulf menhaden landings from 2003 to the present were generally within the range of the projected equilibrium landings (i.e., within confidence intervals) at both the ERP target and threshold values except for three recent years.
Following an assessment of Antarctic krill (Euphausia superba) in the Scotia Sea, CCAMLR established a precautionary catch limit of 4 million tonnes and further adopted 15 small-scale management units (SSMUs). The intent was to subdivide the precautionary catch limit for krill among the SSMUs so as to preclude the inadvertent concentration of catches in a small portion of the surveyed area. Five options for allocating the catch limit among the SSMUs in the Scotia Sea are presented in this paper. The first four are static allocations where the allotment of catch to an SSMU is proportional to: (i) the historical catch within the SSMU; (ii) estimated predator demand in the SSMU; (iii) estimated standing stock of krill in the SSMU; and (iv) standing stock less predator demand in the SSMU. The fifth option is a dynamic allocation based on land-based predator monitoring conducted just prior to, or early in, the fishing season. For the purposes of illustration and comparison between the options, parameter estimates are made using available data, although it is recognised that considerable refinement of these estimates is possible. Qualitative conclusions are that: under the first two options a substantial portion (>65%) of the catch limit would be allocated to three or less of the SSMUs adjacent to large concentrations of land-breeding predators; under options (iii) and (iv) a similar portion of the catch limit would be directed to pelagic SSMUs beyond the foraging range of these predators but into areas where krill fishing has not regularly occurred; and under option (v), an example of an adjustable catch limit dependent on the results of ecosystem monitoring, the fishery would be restricted in some of its traditional fishing grounds during years of low krill availability. Under all five options there would be little effect on the existing fishery. However, as catches increase, a trade-off may be drawn between options that displace the fishery from its current operating area, but reduce the potential for contravening the terms of the Convention, and options that do not displace the fishery, but are likely to contravene the terms of the CCAMLR Convention.
A potential method is presented for combining data collected as part of the CCAMLR ecosystem monitoring program (CEMP) into a single index for each of predator, prey and environmental parameters. The paper is divided into four main parts. The first part develops the proposed method of forming summary indices, which is based on the usual theory of multivariate statistics and takes into account the covariance between parameters. The second part reports on a Monte Carlo simulation study that examines the robustness of the indices to missing data and the degree of correlation between parameters. These trials show that missing values were unlikely to be a problem for time series of parameters that are highly correlated (>0.6). Criteria for inclusion of parameters in the indices are discussed when parameters are moderately or poorly correlated. The third part uses further simulation tests to examine the power of the statistical procedure adopted by WG-EMM in 1996 for identifying anomalies in CEMP parameters. The power of the procedure to detect anomalies was found to fall to low levels once more than a few anomalous values have appeared in the data. An alternative procedure, using estimates of the mean and variance of baseline time series, was found to have consistently better statistical power regardless of the accumulation of anomalies. The last section outlines an approach to the further development of CEMP indices for application in CCAMLR.
SUMMARY: This paper details the mismatch between human fisheries and the behaviour that has evolved to fit pela- gic fishes to their niche. Behavioural adaptations of pelagic fish in feeding. spawning. migration and schooling arc dri- ven by the opportunity to exploit high levels of planktonic production: the highest levels are intrinsically patchy. On an annual scale. the mismatch generates volatility. range reduction and catchability-led stock collapse (CALSC). On a time scale of decades. the human response to uncertainty in pelagic fisheries has been to develop ever more effective levels of fish catching technology. Three quantitative models or catchability collapse are explored. The nonequilibrium Schaefer surplus production model is used for baseline comparisons: catch-per-unit-effort is directly proportional to stock abundance and the catchability of fish is constant. This model is r~markably resilient against rapid stock collap- se. In the Csirke-MacCall model. catchability increases with decreasing -abundance and the stock is led into a CALSC at catch rates only slightly above the Schaefer MSY. This paper introduces a new model in which catch-per-unit-effort is constant while catchability is directly proportional to stock size. the opposite of standard fishery theory but congruent with the effects of high-technology fisheries. In this model CALSC can occur very rapidly. The social behaviour that makes CALSC possible is a behavioural response that can act. in concert with adverse environmental change. to exa- cerbate stock collapse. Management of pelagic fisheries must recognise that the behaviour or pelagic fishes. tuned by evolution ror persistence in this volatile niche. can make human exploitation of this resource a fragile enterprise.
Responsible fisheries management is of increasing interest to the scientific community, resource managers, policy makers, stakeholders and the general public. Focusing solely on managing one species of fish stock at a time has become less of a viable option in addressing the problem. Incorporating more holistic considerations into fisheries management by addressing the trade-offs among the range of issues involved, such as ecological principles, legal mandates and the interests of stakeholders, will hopefully challenge and shift the perception that doing ecosystem-based fisheries management is unfeasible. Demonstrating that EBFM is in fact feasible will have widespread impact, both in US and international waters. Using case studies, underlying philosophies and analytical approaches, this book brings together a range of interdisciplinary topics surrounding EBFM and considers these simultaneously, with an aim to provide tools for successful implementation and to further the debate on EBFM, ultimately hoping to foster enhanced living marine resource management.
Small pelagic fish are termed “wasp-waist” species as they dominate mid trophic levels and comprise relatively few species but attain large abundances that can vary drastically in size. They have been found to exert top-down control on their prey species and bottom-up control on their predators and, in this way, appear to induce unsuspected ecosystem dynamics. Largely based on model results, this chapter explores these effects and associated dynamics, not only illustrating the importance of small pelagic fish in structuring marine ecosystems, but also revealing the consistency of the role of small pelagic fish across various upwelling systems in which they play key roles. The Northern and Southern Benguela, Southern Humboldt, South Catalan Sea and North and Central Adriatic Sea ecosystems are compared in terms of the importance and role of small pelagic fish using information gained from landings and ecological models. Trophic level of the catch, the Fishing-in-Balance (FiB) index and the ratio of pelagic:demersal fish are calculated from reported landings. Sums of all flows to detritus are compared across modelled ecosystems. Models of the Southern Benguela, Southern Humboldt and South Catalan Sea are used to perform two simulations: (1) closure of fisheries on small pelagic fish and (2) collapse of small pelagic fish stocks, to further explore the roles of small pelagic fish in the dynamics of these ecosystems. Tracking pelagic:demersal fish catch and biomass ratios over time is a means of detecting collapses in the small pelagic fish stocks, and comparing these ratios across ecosystems highlights the greater importance of small pelagic fish in the Humboldt compared to other ecosystems.