Lower Trophic Level Fish Research Articles

Physiological, temporal, and environmental determinants of dry energy densities of low trophic-level fishes in the Gulf of Mexico

Low trophic-level fishes provide a link to higher trophic-level animals, including birds, mammals, and economically valuable fishes. Despite their role, the dry energy density (DED) of these fishes and its variability have not been described in the northern Gulf of Mexico (nGOM). To address this, we describe species-specific DED for four fish species in the nGOM: Atlantic Croaker (Micropogonias undulatus), Gulf Menhaden (Brevoortia patronus), White Trout (Cynoscion arenarius), and Bay Anchovy (Anchoa mitchilli). We investigated the impacts of body length, life stage (juvenile and adult), month of collection, and river discharge from the Mississippi River to determine the response of DED for Atlantic Croaker and Gulf Menhaden. Using bomb calorimetry, we found that the DED of Atlantic Croaker ranged from 3021 to 6445 calories/g (mean = 4524 ± 646 calories/g SD, n = 129), Gulf Menhaden DED ranged from 2578 to 6821 calories/g (mean = 5069 calories/g ± 794 SD, n = 193), White Trout DED ranged from 3118 to 4581 calories/g (mean = 4120 calories/g ± 358 SD, n = 30), and Bay Anchovy DED ranged from 3925 to 4387 calories/g (mean = 4261 ± 126 calories/g SD, n = 74). The mean DED of Gulf Menhaden and Atlantic Croaker varied and was at a minimum during the fall. The DED of Gulf Menhaden and Atlantic Croaker were linearly, positively, and significantly (α = 0.05) related to fork length (R2 = 0.23 and R2 = 0.32, respectively). The flow rate of the Mississippi River was not a significant predictor of the DED of juvenile or adult Gulf Menhaden but was a significant predictor of the DED of adult Atlantic Croaker (p < 0.001, R2 = 0.04). The species-specific energy density values and the variations due to the month of collection, environmental conditions, and physiological variation will serve to inform ecosystem models.

Half-century trends of radioactivity in fish from Danish areas of the North Sea, Kattegat, and Baltic Sea

This work reports comprehensive time-series datasets over the past 50 years for natural (210Po) and anthropogenic (134Cs and 137Cs) radionuclides in three fish species (cod, herring and plaice) from Danish marine areas covering the North Sea, Kattegat, and Baltic Sea. Impact from the global fallout of atmospheric nuclear weapons testing, radioactive discharges from the European nuclear reprocessing plants and release from Chernobyl accident are clearly detected in the fish samples. While 210Po concentrations in each fish species demonstrated comparable levels across the three regions without notable temporal trends, significantly higher median 210Po concentration was observed in the lower trophic level fish, namely herring and plaice, compared to cod. In contrast, 137Cs concentrations in all three species steadily decrease over time after the Chernobyl-attributed peaks in late 1980s in the entire study area, whereas 137Cs always demonstrated higher concentrations in cod than herring and plaice. Our calculated concentration factors (CFs) for 137Cs in this work indicate that the mean CFs for 137Cs over the past 50 years are significantly different across the three species, following the order of cod < herring < plaice. Based on the time-series data, ecological half-lives (Teco) of 137Cs in fish from Danish marine areas were estimated to evaluate the long-term impact of anthropogenic radioactive contamination in different regions. Our results indicate no significant difference in Teco across different fish species, whereas the weighted mean Teco for fish in the Baltic Sea (29.3 ± 3.9 y) is significantly longer than those of the North Sea (9.8 ± 0.9 y) and Kattegat (11.7 ± 1.2 y), reflecting the strong ‘memory effect’ of the Baltic Sea due to its slow water renewal. However, the dose assessment demonstrates that the contribution of the natural radionuclide 210Po to ingestion dose from fish consumption is 1–2 order of magnitude higher compared to that of 137Cs.

Human and dog Bayesian dietary mixing models using bone collagen stable isotope ratios from ancestral Iroquoian sites in southern Ontario

Under the archaeological canine surrogacy approach (CSA) it is assumed that because dogs were reliant on humans for food, they had similar diets to the people with whom they lived. As a result, the stable isotope ratios of their tissues (bone collagen and apatite, tooth enamel and dentine collagen) will be close to those of the humans with whom they cohabited. Therefore, in the absence of human tissue, dog tissue isotopes can be used to help reconstruct past human diets. Here δ13C and δ15N ratios on previously published dog and human bone collagen from fourteenth-seventeenth century AD ancestral Iroquoian village archaeological sites and ossuaries in southern Ontario are used with MixSIAR, a Bayesian dietary mixing model, to determine if the dog stable isotope ratios are good proxies for human isotope ratios in dietary modeling for this context. The modeling results indicate that human dietary protein came primarily from maize and high trophic level fish and dogs from maize, terrestrial animals, low trophic level fish, and human feces. While isotopes from dog tissues can be used as general analogs for human tissue isotopes under CSA, greater insights into dog diets can be achieved with Bayesian dietary mixing models.

Bioaccumulation and health risk assessment of phthalate esters in cultured low trophic level fish feded with food waste-based diets

The present study aimed at using different types of food waste as a protein source for the fish feeds to produce safe and quality fish. The results showed the concentrations of ∑PAEs in grass crap (0.24 μg g−1 ww) and bighead carp (0.15 μg g−1 ww) fed with Food waste B feeds (mainly containing fruit, vegetable and cereal waste) was significantly lower than those fed Food waste A feeds (mainly containing meat waste) and control feeds (p<0.05), and the highest ∑PAEs concentration (1.75 μg g−1 ww) was found in the mud carp fed with control feeds in experimental ponds (p<0.05). In addition, there was no biomagnification of PAEs in the food chains within the ponds. The health risk assessment results showed no non-carcinogenic and carcinogenic risks from the PAEs via ingestion of the fish fed with food waste feeds for the local residents.

Understanding Food Web Mercury Accumulation Through Trophic Transfer and Carbon Processing along a River Affected by Recent Run-of-river Dams.

Unlike large dams which favor methylation of Hg in flooded soils over long periods, run-of-river dams are designed to flood a limited area of soils and are therefore not expected to significantly affect mercury (Hg) cycling or carbon processing. We studied the Hg and carbon cycles within food webs from several sectors along the Saint-Maurice River, Quebec, Canada, that differ in how they are influenced by two run-of-river dams and other watershed disturbances. We observed peak Hg concentrations in fish five-year postimpoundment, but these levels were reduced three years after this peak. Methylmercury concentrations in low trophic level fish and invertebrates were related to their carbon source (δ13C) rather than their trophic positions (δ15N). Biomagnification, measured by trophic magnification slopes, was driven mainly by methylmercury concentrations in low-trophic level organisms and environmental factors related to organic matter degradation and Hg-methylation. River sectors, δ13C and δ15N, predicted up to 80% of the variability in food web methylmercury concentrations. The installation of run-of-river dams and the related pondages, in association with other watershed disturbances, altered carbon processing, promoted Hg-methylation and its accumulation at the base of the food web, and led to a temporary increase in Hg levels in fish.

The influence of nutrient loading on methylmercury availability in Long Island estuaries.

Estuaries provide critical habitat for food webs supporting fish and shellfish consumed by humans, but estuarine ecosystem health has been threatened by increases in nitrogen loading as well as inputs of the neurotoxin, mercury (Hg), which biomagnifies in food webs and poses risk to humans and wildlife. In this study, the effects of nutrient loading on the fate of Hg in shallow coastal estuaries were examined to evaluate if their interaction enhances or reduces Hg bioavailability in sediments, the water column, and concentrations in lower trophic level fish (Fundulus heteroclitus and Menidia menidia). Multiple sites were sampled within two human impacted coastal lagoons, Great South Bay (GSB) and Jamaica Bay (JB), on the southern coast of Long Island, NY, United States of America (U.S.A.). Carbon (C), nitrogen (N), sulfur (S), Hg, and methylmercury (MeHg) were measured in surface sediments and the water column, and total Hg (THg) was measured in two species of forage fish. Minimal differences were found in dissolved and particulate Hg, dissolved organic carbon (DOC), and salinity between the two bays. Across lagoons, concentrations of chlorophyll-a were correlated with total suspended solids (TSS), and water column THg and MeHg was largely associated with the particulate fraction. Methylmercury concentrations in particulates decreased with increasing TSS and chlorophyll-a, evidence of biomass dilution of MeHg with increasing productivity at the base of the food chain. Water column Hg was associated with THg concentrations in Atlantic silversides, while mummichog THg concentrations were related to sediment concentrations, reflecting their different feeding strategies. Finally, higher nutrient loading (lower C:N in sediments) while related to lower particulate concentrations coincided with higher bioaccumulation factors (BAF) for Hg in both fish species. Thus, in shallow coastal lagoons, increased nutrient loading resulted in decreased Hg concentrations at the base of the food web but resulted in greater bioaccumulation of Hg to fish relative to its availability in algal food.

Valorisation of aquaculture effluents with microalgae: The Integrated Multi-Trophic Aquaculture concept

One of the main problems of aquaculture is the environmental impact of its effluents, which are rich in particulate and dissolved nutrients from undigested feed and faeces. In intensive aquaculture systems the main dissolved nutrient present in effluents is ammonium, which is converted into nitrate through nitrification in aerobic bacterial filters. Microalgae can substitute bacteria by efficiently harvesting and recycling nutrients. The main advantage of the use of microalgae is the obtainment of biomass that can be valorised by using it as feed for other aquatic organisms in a process known as Integrated Multi-Trophic Aquaculture (IMTA). Cultured microalgae can be used to feed low trophic level fish, herbivorous fish and molluscs, which can in turn be sold on the market, as well as being a source of valuable chemicals. Nevertheless, most IMTA studies have been focused on the use of macroalgal biofiltration. The incorporation of microalgal culture with controlled cultivation conditions as biofilters in land-based IMTA systems presents high potential because they achieve more efficient photosynthetic rates and higher growth rates and present better biochemical composition than macroalgae. The present review comprises information on the microalgal-based IMTA systems described so far in the literature. Additionally, microalgae culture methods that are applied to aquaculture wastewater treatment, such as periphyton, microalgal-bacterial consortiums and cell immobilization are assessed.

Disentangling seafood value chains: Tourism and the local market driving small-scale fisheries

Identifying socio-economic drivers of small-scale fisheries is a fundamental step to understand impacts and pressures on fishery resources, and the behaviour of seafood trade actors. It is especially relevant for developing countries where such information is usually lacking and fisheries management is greatly needed. To address this gap, this study maps the structure of value chains of fish and marine invertebrates caught by small-scale fisheries from São Vicente, Cape Verde (West Africa), and examines the main socio-economic drivers behind the seafood trade on the island. Specifically, it shows how drivers, such as tourism and the local market, shape the preferences for certain species and how they affect the distribution of income among actors involved in the seafood trade. To collect this information, interviews were done with fishers, small-scale traders, market vendors, and restaurant owners, in all fishing communities of the island of São Vicente, in 2015. Tourism and the local market drive the exploitation of a wide variety of marine species, from small demersal low trophic level fish and marine invertebrates, to large pelagic high trophic level fish species. Moreover, the local seafood market, and especially tourism dynamics, contribute to the unequal distribution of income among actor groups, benefiting mostly restaurant owners due to their direct access to tourist consumers. Such findings have implications for local fishery resources management, food security, and fishing communities’ livelihoods.

Processes and pathways of ciguatoxin in aquatic food webs and fish poisoning of seafood consumers

Ciguatera food poisoning (CFP) is widespread in tropical and sub-tropical waters, and it is the most common food poisoning caused by marine biotoxins. The toxins involved, ciguatoxins, are produced by certain dinoflagellates of the genus Gambierdiscus, and undergo biotransfer and biomagnification up the food web to planktivorous and ultimately, top predator fishes. In this paper, we reviewed the factors and processes that regulate the production of ciguatoxins, the ecological distribution and the pathways of their biotransfer, and fish consumption guidelines to prevent ciguatera-related food poisoning. Warm waters are commonly suggested as the most important factor that enhances toxic algal blooms and ciguatoxin production. Ecological distribution of ciguatoxic fish shows great regional specificity. In most endemic areas, carnivores such as groupers and other large fish have higher toxicity than their herbivorous and smaller counterparts, supporting the food chain hypothesis proposed by J.E. Randall (J.E. Randall, Bull. Mar. Sci. 8(3): 236–267, 1958); while in other areas, for example, French Polynesia, the opposite situations also exist, questioning the biomagnification hypothesis. Some countries and regions have taken measurements to prevent ciguatera poisoning through consumption guidelines. In this review, we look at some of the measures that could be used to prevent poisoning, while encouraging people to consume fish. For example, choosing smaller and lower trophic level fish are likely to be safer to consume. We suggest an approach to maintain better databases on ciguatera cases to instruct people on fish consumption safety, and develop a general guideline for fish consumption to reduce CFP.

Branched chain fatty acid content of edible portions of northeastern U.S. freshwater fish

IntroductionBranched chain fatty acids (BCFA) are major components of skin/membranes across various mammals and bacterial genera. BCFA are bioactive and alter gut microbiota. Intake of BCFA, mainly from dairy/beef was estimated at 500 mg per day in US. Our goal was to investigate BCFA levels in common freshwater fish species.MethodsWe captured over 20 fish species from several lakes and streams in New York and Pennsylvania. We dissected larger fish and sampled muscle tissue from dorsal and caudal fins as well as the belly and the skin. Smaller fish were entirely grinded before processing. All samples were extracted, saponified and methylated. BCFA profiles were analyzed using gas chromatography mass spectrometry.ResultsBCFA content varied across species and ranged from 0.6–2.7%, w/w of total fatty acids in fish muscle samples, with an overall mean of 1.2%. Some low trophic level fishes, such as killifish, rainbow smelt, and juvenile pumpkinseed, had over 2% BCFA while some common game fish species white perch, yellow perch, smallmouth bass, and walleye had about 1% BCFA, w/w or less of total fatty acids. A few low trophic level fishes such as fantail darter in the same perch family as yellow perch and walleye had low BCFA levels, suggesting influences related to phylogenetic structure. Skin contained between 1.2–3.2% BCFA, w/w of total fatty acids. Across all species sampled, skin samples had higher BCFA levels compared to muscle samples. The overall fatty acid profile, including BCFA was similar across muscles from different parts of a fish. The major BCFA in fish are iso‐15:0, anteiso‐15:0, iso‐16:0, iso‐17:0 and anteiso‐17:0. Trace amounts of iso‐13:0, anteiso‐13:0, iso‐14:0, iso‐18:0, anteiso‐19:0 and iso‐20:0 were also detected.ConclusionMany low‐trophic‐level fishes had BCFA levels comparable with dairy products and their skin samples showed higher BCFA content than muscle.Support or Funding InformationNIH R01 AT007003

Shift in a large river fish assemblage: body-size and trophic structure dynamics.

As the intensity and speed of environmental change increase at both local and global scales it is imperative that we gain a better understanding of the ecological implications of community shifts. While there has been substantial progress toward understanding the drivers and subsequent responses of community change (e.g. lake trophic state), the ecological impacts of food web changes are far less understood. We analyzed Wabash River fish assemblage data collected from 1974-2008, to evaluate temporal variation in body-size structure and functional group composition. Two parameters derived from annual community size-spectra were our major response variables: (1) the regression slope is an index of ecological efficiency and predator-prey biomass ratios, and (2) spectral elevation (regression midpoint height) is a proxy for food web capacity. We detected a large assemblage shift, over at least a seven year period, defined by dramatic changes in abundance (measured as catch-per-unit-effort) of the dominant functional feeding groups among two time periods; from an assemblage dominated by planktivore-omnivores to benthic invertivores. There was a concurrent increase in ecological efficiency (slopes increased over time) following the shift associated with an increase in large-bodied low trophic level fish. Food web capacity remained relatively stable with no clear temporal trends. Thus, increased ecological efficiency occurred simultaneous to a compensatory response that shifted biomass among functional feeding groups.

Replacing fish meal by food waste to produce lower trophic level fish containing acceptable levels of polycyclic aromatic hydrocarbons: Health risk assessments

This study aimed at using different types of food wastes (mainly containing cereal [food waste A] and meat meal [food waste B]) as major sources of protein to replace the fish meal used in fish feeds to produce quality fish. The traditional fish farming model used to culture low trophic level fish included: bighead, (Hypophthalmichthys nobilis), grass carp, (Ctenopharyngodon idellus), and mud carp, (Cirrhinus molitorella) of omnivorous chain. The results indicated that grass carp and bighead carp fed with food waste feeds were relatively free of PAHs. The results of health risk assessment showed that the fish fed with food waste feeds were safe for consumption from the PAHs perspective.

Overfishing and the replacement of demersal finfish by shellfish: an example from the English Channel.

The worldwide depletion of major fish stocks through intensive industrial fishing is thought to have profoundly altered the trophic structure of marine ecosystems. Here we assess changes in the trophic structure of the English Channel marine ecosystem using a 90-year time-series (1920–2010) of commercial fishery landings. Our analysis was based on estimates of the mean trophic level (mTL) of annual landings and the Fishing-in-Balance index (FiB). Food webs of the Channel ecosystem have been altered, as shown by a significant decline in the mTL of fishery landings whilst increases in the FiB index suggest increased fishing effort and fishery expansion. Large, high trophic level species (e.g. spurdog, cod, ling) have been increasingly replaced by smaller, low trophic level fish (e.g. small spotted catsharks) and invertebrates (e.g. scallops, crabs and lobster). Declining trophic levels in fisheries catches have occurred worldwide, with fish catches progressively being replaced by invertebrates. We argue that a network of fisheries closures would help rebalance the trophic status of the Channel and allow regeneration of marine ecosystems.

Trophic flow structure of the Danajon ecosystem (Central Philippines) and impacts of illegal and destructive fishing practices

A trophic model of the shallow Danajon Bank, in the Central Visayas, Philippines was developed using a mass-balance approach (Ecopath) to describe the system characteristics and fisheries interactions. The Ecopath model is composed of 37 functional groups and 17 fishing fleet types reflecting the high diversity of catches and fishing operations in the Danajon Bank. Collectively, the catch is dominated by lower trophic level fish and invertebrates as reflected in the mean trophic level of the fishery (2.95). The low biomass and high exploitation levels for many upper trophic level groups and the little evidence for strong natural physical disturbances suggest that top-down fishery is the main driver of system dynamics. The mixed trophic impacts (MTI) analysis reveals the role of the illegal and destructive fishing operations in influencing the ecosystem structure and dynamics. Furthermore, the illegal fisheries' estimated collective annual harvest is equivalent to nearly a quarter of the entire municipal fisheries catch in the area. Improved fisheries law enforcement by the local government units to curb these illegal and destructive fishing operations could substantially increase the potential gains of the legal fisheries.

Application of food waste based diets in polyculture of low trophic level fish: Effects on fish growth, water quality and plankton density

Food waste was collected from local hotels and fish feed pellets were produced for a 6months long field feeding trial. Three types of fish feed pellets (control diet: Jinfeng® 613 formulated feed, contains mainly fish meal, plant product and fish oil; Diet A: food waste based diet without meat and 53% cereal; Diet B: food waste based diet with 25% meat and 28% cereal) were used in polyculture fish ponds to investigate the growth of fish (grass carp, bighead and mud carp), changes in water quality and plankton density. No significant differences in the levels of nitrogen and phosphorous compounds of water body were observed between 3 fish ponds after the half-year feeding trial, while pond receiving Diet A had the highest density of plankton. The food waste combination of Diet B seems to be a better formulation in terms of the overall performance on fish growth.

Biological aspects and catch trends of elasmobranchs in the inshore waters of Goa, west coast of India

Despite being the top predators Elasmobranchs are dwindling due to excessive fishing pressure. However, very few studies along Indian coasts have focused on their eco-biological aspects. The present investigation comprising 158 trawl samples (220 h effort) along the nearshore fishing grounds of Goa revealed that the elasmobranch population comprised 10 species (2 sharks, 6 rays and 2 skates). Analysis of spatial variation revealed significant variations between the regions (abundance, α = 0.001, P= 0.000191; weight, α = 0.001, P = 2.14E-08) suggesting high catches along southern region, owing to lesser fresh water discharge due to absence of major estuarine system. Assessment of size class indicated that juveniles dominated the elasmobranch population with few stray occurrences of adults. Dietary analysis of the three commonly observed species revealed the dominance of teleosts (45.95% IRI), followed by crustaceans (40.19% IRI). Analysis of the catch trends (1969–2004) of elasmobranchs in this region indicated meagre contribution (0.05–5.04%) to the total marine fish landings of Goa. Further, the catch trends displayed decrease in recent times suggesting reduction in trophic level of the regional fishery perhaps caused by fishing out of carnivores coupled with increased catches of low trophic level fishes as evidenced in the present study. These findings have implications for the trophic web dynamics of the coastal waters, which in turn affect the coastal fisheries of the region.

Impact evaluation of spear fishing on fish communities in an urban area of São Miguel Island (Azores Archipelago)

AbstractThis study was conducted in São Miguel Island (Azores archipelago) providing the first evidence from Macaronesia of spear fishing impacts on fish communities. The shoreline was monitored during 10 months by access point surveys where 220 fishers were interviewed and 27 target fish species were identified. Mean sizes of top predators and highly vulnerable species were generally less than the respective minimum first maturation length. Species intrinsic vulnerability was moderate with an average of 46.7 (max. 100). There are indications that spear fishers, in the absence of high trophic level and larger species, target smaller and lower trophic level fish, atypical of a highly selective fishery. Daily bag limits were not respected in 36.9% of spear fishing operations and 59% of the catch from the area was illegally sold, a practice likely to have negative consequences for the commercial sector.

Impacts of Fishing Low–Trophic Level Species on Marine Ecosystems

Low-trophic level species account for more than 30% of global fisheries production and contribute substantially to global food security. We used a range of ecosystem models to explore the effects of fishing low-trophic level species on marine ecosystems, including marine mammals and seabirds, and on other commercially important species. In five well-studied ecosystems, we found that fishing these species at conventional maximum sustainable yield (MSY) levels can have large impacts on other parts of the ecosystem, particularly when they constitute a high proportion of the biomass in the ecosystem or are highly connected in the food web. Halving exploitation rates would result in much lower impacts on marine ecosystems while still achieving 80% of MSY.

Unexpected patterns of fisheries collapse in the world's oceans

Understanding which species are most vulnerable to human impacts is a prerequisite for designing effective conservation strategies. Surveys of terrestrial species have suggested that large-bodied species and top predators are the most at risk, and it is commonly assumed that such patterns also apply in the ocean. However, there has been no global test of this hypothesis in the sea. We analyzed two fisheries datasets (stock assessments and landings) to determine the life-history traits of species that have suffered dramatic population collapses. Contrary to expectations, our data suggest that up to twice as many fisheries for small, low trophic-level species have collapsed compared with those for large predators. These patterns contrast with those on land, suggesting fundamental differences in the ways that industrial fisheries and land conversion affect natural communities. Even temporary collapses of small, low trophic-level fishes can have ecosystem-wide impacts by reducing food supply to larger fish, seabirds, and marine mammals.

Total Mercury Distribution in Different Fish Species Representing Different Trophic levels from the Atlantic Coast of Ghana

Concentrations of total mercury (Hg) were measured in the edible muscle tissues of different fish species representing different trophic levels from the Atlantic Coast of Ghana using Cold Vapour Atomic Absorption Spectrophotometry (CVAAS). Mercury concentrations were gener-ally found to increase with trophic levels. The concentrations of the metal (Hg) were highest (mean=0.093 &mu;g g-1) in high trophic level predatory fish, followed by middle trophic level preda-tory fish (mean=0.063 &mu;g g-1) and low trophic level fish (mean=0.047 &mu;g g-1). However the differ-ences were not significant at the 0.05 level according to ANOVA. All fish species analysed in this study had total mercury concentrations (range: 0.001-0.278 &mu;g g-1) less than the FAO/WHO limit of 0.5 &mu;g g-1 wet weight. The low concentrations of mercury in the fish species obtained in this study do not appear to contribute any significant mercury exposure to the general popula-tion; and suggest a relatively clean marine environment that has not yet been significantly im-pacted by mercury contamination probably due to minimal industrial activity in the region.Keywords: Mercury; Fish; Atlantic Coast; Ghana; Trophic level