Abundance Of Demersal Fishes Research Articles

Feeding ecology of redfish (Sebastes sp.) inferred from the integrated use of fatty acid profiles as complementary dietary tracers to stomach content analysis.

In the northern Gulf of St. Lawrence (nGSL), redfish (Sebastes mentella and Sebastes fasciatus combined) are at record levels of abundance following the strong recruitment of three consecutive cohorts in 2011-2013 and have become by far the most abundant demersal fish in the region. Understanding redfish trophic relationships is essential for the effective management and conservation of species in the nGSL ecosystem. To date, description and quantification of redfish diet in the region have been restricted to conventional stomach content analysis (SCA). Using analysis of fatty acid (FA) profiles as complementary dietary tracers, the authors conducted multivariate analyses on 350 livers of redfish which were collected in combination with stomach contents during a bottom-trawl scientific survey in August 2017. The predator FA profiles were compared to those of eight different redfish prey types identified as dietary important with SCA. Results suggested similitude between SCA and FA results, with zooplankton prey being more related to small (<20 cm) and medium (20-30 cm) redfish (16:1n7, 20:1n?, 22:1n9 and 20:5n3) than large (≥30 cm) ones, whereas shrimp prey seemed more related to large redfish size classes (18:2n6 and 22:6n3) relative to the small and medium ones. Although the SCA offers a glimpse in the diet only based on the most recently consumed prey, analysis of FA profiles provides a mid-term view indicating pelagic zooplankton consumption on calanoid copepod and confirming high predation pressure on shrimp. This study constitutes the first attempt of combining FA with SCA to assess the diet of redfish, highlights the benefits of FA as a qualitative tool and suggests improvements for future studies.

Jan Mayen—a new spawning and fishing area for Atlantic cod Gadus morhua

In 2018, commercially exploitable concentrations of Atlantic cod Gadus morhua were found on the shelf around the Arctic island Jan Mayen (7 1°N, 8–9 °W) and in 2019–2021 an exploratory cod fishery with longline was carried out in the area. The total catch in the period 2018–2021 was 1737 tonnes. The first records of cod fishery in the Jan Mayen area are from the early 1930s but catches before 2018 were minimal. In 2019–2020 cod spawning was documented in this area for the first time. Catches in 2019 and 2020 were dominated by cod between 70 and 100 cm, while in 2021 the main part of the catches was cod between 60 and 100 cm. Catch rates were highest in autumn. We summarize the history of cod observations and the experience from the recent exploratory fishery in this shelf area where there has been no regular monitoring of demersal fish abundance. Further, we consider possible links with cod stocks in other Arctic and sub-Arctic areas and discuss the occurrence of cod in the Jan Mayen area in relation to the biology and recent development of other cod stocks.

Recent warming causes functional borealization and diversity loss in deep fish communities east of Greenland

AbstractAimWe assessed temporal trends in functional diversity of the deep‐sea demersal fish communities of East Greenland to characterize ecological responses to rising sea temperatures.LocationThe study region encompasses a shelf and slope area located offshore between 63°N and 66°N, east of Greenland.MethodsA unique dataset of demersal fish abundance covering a depth range of 1500 m over 18 years was combined with a fish trait dataset which included a mix of quantitative and categorial traits that characterized species' morphology, feeding strategy, habitat, and life history. We analysed the species by trait matrix using principal component analysis (PCA). To investigate trait patterns across the communities (sites), community weighted mean (CWM) traits were calculated and analysed using PCA. Further, depth specific and temporal trends in functional diversity indices were calculated.ResultsWe found signs of a taxonomic and functional borealization, associated with a loss in functional diversity, down to 1000 m, characterized by an increase in mobile generalists and a decrease in bottom dwelling benthivores.Main conclusionsThe increased dominance of boreal species traits was not sufficient to compensate for the loss of Arctic species traits leading to declining functional diversity. The decrease in functional diversity may negatively affect ecosystem robustness to environmental change. These responses are most likely not unique to this study area and call for more attention to ecosystem considerations in climate change management strategies in the deep‐sea.

Food Choice and Prey Selection by Great Cormorants Phalacrocorax carbo in a Shallow Coastal Zone in the Dutch Delta Area: Importance of Local Flatfish Stocks

Coastal breeding Great Cormorants Phalacrocorax carbo foraging in a shallow part of the Dutch North Sea preyed upon abundant marine demersal fish species. In 2010–2012 intensive fish surveys were performed in the Voordelta area and in 2009–2015 Cormorant pellets were sampled in the breeding colony of Breede Water, Voorne, four times per year between March and September. In total 48 fish species were detected in the diet, 38 being marine species. Mainly flatfish were consumed, and European Plaice, Common Dab and Common Sole were the most important prey according to fish mass. Experimental trawling revealed 65 species of fish of which gobies, Herring, Whiting, Sprat, European Plaice and Common Dab were the most abundant. Compared to the trawl data, Cormorants showed a preference for Common Dab and Common Sole and for other solitary bottom fish like sandeels and Shorthorn Sculpin. These species were all common in the area. With respect to uncommon and rare species, no preferential selection was recorded. Densities of flatfish were highest in foraging areas closest to the breeding colony and possible depletion effects were only recorded in Common Dab. This diurnal species was already being preyed upon early in the season. Nocturnal foraging habits in other flatfish species, in combination with burrowing behaviour and rounded body shape are effective anti-predator traits and this was reflected in lower frequencies of these species in the Cormorants' diet. Consumption of freshwater fish by Cormorants at the beginning of the breeding period enabled an early start to breeding, and the increasing availability of flatfish in late spring matched the peak demand of rearing nestlings. The almost exclusive predation on flatfish was probably caused by the near-bottom foraging behaviour of most Cormorants and this habit made the birds feed on other abundant demersal fish species as well, such as Whiting, sandeels, Shorthorn Sculpin, Lesser Weever and dragonet species. And although numerous in the system, this bottom-oriented feeding behaviour of Cormorants therefore resulted in a very limited predation on pelagic fish species. In total we estimate an annual extraction by Cormorants of some 100 tonnes of fish being c. 77,600 kg flatfish and c. 20,700 kg other marine fish. Although with a foraging range partly outside the coastal zone, the extraction of fish by Harbour Seals Phoca vitulina and Grey Seals Halichoerus grypus outnumbered that of Cormorants by a factor of 9. As seals are known flatfish consumers, this suggests that there is competition between mammalian and avian predators on demersal fish stocks in the coastal zone.

Padrões da assembleia de peixes em uma baía subtropical do sul do Brasil

Abstract: In this study, the relationship between fish assemblage structure and environmental factors was analyzed in a bay in southern Brazil. Fish were collected every two months between February and December 2002 at six sampling sites using bottom trawl nets. Abiotic data (salinity, temperature, rainfall, and depth) and biotic data (number of individuals, biomass, and total length of individuals from each species) were obtained. In total, 56 fish species representing 27 families were collected. Assemblage structure varied with seasonality, as was evidenced by the variation in temperature and rainfall in each season. Catches showed a high abundance of demersal fishes, particularly Genidens genidens, Eucinostomus gula, and E. argenteus.

Diet of dominant demersal fish species in the Baltic Sea: Is flounder stealing benthic food from cod?

Knowledge about ecological interactions between species is of paramount importance in ecology and ecosystem-based fisheries management. To understand species interactions, studies of feeding habits are required. In the Baltic Sea, there is good knowledge of the diet of cod, but little is known about the diet of flounder, the second most abundant demersal fish in the region. In this study, we investigated the diets of cod and flounder for the first time using stomach content data collected simultaneously in 2015-2017 over a large offshore area of the southern Baltic Sea. The diet of flounder was relatively constant between sizes and seasons and was dominated by benthos, with a high proportion in weight of the benthic isopodSaduria entomon. The diet of cod differed between seasons and showed an ontogenetic shift with a relative decrease of benthic prey and an increase of fish prey with size. Historic diet data of cod were used to explore cod diet changes over time, revealing a shift from a specialized to generalist feeding mode paralleled by a large relative decline in benthic prey, especiallyS. entomon. Flounder populations have increased in the past 2 decades in the study area, and therefore we hypothesized that flounder have deprived cod of important benthic resources through competition. This competition could be exacerbated by the low benthic prey productivity due to increased hypoxia, which could contribute to explaining the current poor status of the Eastern Baltic cod. The results of this study point to the importance of including flounder in multispecies end ecosystem models.

Trophic interactions between the 11 most abundant demersal fish species on the Pacific coast of central Mexico

We describe the diet, feeding strategy, and trophic interactions between the 11 most abundant demersal fish species on the Pacific coast of central Mexico during both the warm and cold seasons. A total of 4,547 stomachs were collected, with 1,921 empty stomachs being discarded. According to the stomach content analysis, 95 prey items were identified and grouped into 70 food categories belonging to crustaceans, mollusks, fish, polychaetes, and echinoderms. The Smith index value and high prey diversity indicated that the 11 fish species exhibited a generalist opportunistic feeding strategy in both survey seasons. Low values of dietary overlap were recorded, and only a few significant cases of dietary overlap were found in the interaction between some rays (Urotrygonidae) and flatfish species (Pleuronectiformes). The availability and abundance of prey resources in the environment and the generalization of niche breadth allows the demersal predator community of the soft shallow bottoms to coexist without any evident competition for trophic resources.

Evidence for seasonal cycles in deep-sea fish abundances: A great migration in the deep SE Atlantic?

Animal migrations are of global ecological significance, providing mechanisms for the transport of nutrients and energy between distant locations. In much of the deep sea (>200m water depth), the export of nutrients from the surface ocean provides a crucial but seasonally variable energy source to seafloor ecosystems. Seasonal faunal migrations have been hypothesized to occur on the deep seafloor as a result, but have not been documented. Here, we analyse a 7.5-year record of photographic data from the Deep-ocean Environmental Long-term Observatory Systems seafloor observatories to determine whether there was evidence of seasonal (intra-annual) migratory behaviours in a deep-sea fish assemblage on the West African margin and, if so, identify potential cues for the behaviour. Our findings demonstrate a correlation between intra-annual changes in demersal fish abundance at 1,400m depth and satellite-derived estimates of primary production off the coast of Angola. Highest fish abundances were observed in late November with a smaller peak in June, occurring approximately 4months after corresponding peaks in primary production. Observed changes in fish abundance occurred too rapidly to be explained by recruitment or mortality, and must therefore have a behavioural driver. Given the recurrent patterns observed, and the established importance of bottom-up trophic structuring in deep-sea ecosystems, we hypothesize that a large fraction of the fish assemblage may conduct seasonal migrations in this region, and propose seasonal variability in surface ocean primary production as a plausible cause. Such trophic control could lead to changes in the abundance of fishes across the seafloor by affecting secondary production of prey species and/or carrion availability for example. In summary, we present the first evidence for seasonally recurring patterns in deep-sea demersal fish abundances over a 7-year period, and demonstrate a previously unobserved level of dynamism in the deep sea, potentially mirroring the great migrations so well characterized in terrestrial systems.

Drivers of parasite community structure in fishes of the continental shelf of the Western Mediterranean: the importance of host phylogeny and autecological traits

We explored the relationships between features of host species and their environment, and the diversity, composition and structure of parasite faunas and communities using a large taxonomically consistent dataset of host-parasite associations and host-prey associations, and original environmental and host trait data (diet, trophic level, population density and habitat depth vagility) for the most abundant demersal fish species off the Catalonian coast of the Western Mediterranean. Altogether 98 species/taxa belonging to seven major parasite groups were recovered in 683 fish belonging to 10 species from seven families and four orders. Our analyses revealed that (i) the parasite fauna of the region is rich and dominated by digeneans; (ii) the host parasite faunas and communities exhibited wide variations in richness, abundance and similarity due to a strong phylogenetic component; (iii) the levels of host sharing were low and involved host generalists and larval parasites; (iv) the multivariate similarity pattern of prey samples showed significant associations with hosts and host trophic guilds; (v) prey compositional similarity was not associated with the similarity of trophically transmitted parasite assemblages; and (vi) phylogeny and fish autecological traits were the best predictors of parasite community metrics in the host-parasite system studied.

Habitat partitioning by native and alien fishes and decapods in novel habitats of the upper San Francisco Estuary

The rate of alien species introductions is increasing in aquatic ecosystems, but many invaders appear to co-exist with previous residents, resulting in persistent mixed assemblages of non-coevolved organisms. This study focuses on species’ habitat partitioning of edge habitats in the San Francisco Estuary, a highly altered novel ecosystem that supports mixed assemblages of native and alien fishes and macroinvertebrates. We used minnow traps to address two questions about the demersal assemblage along levees in large tidal sloughs: (1) What is the relative abundance of demersal fish and macroinvertebrate species in shallow water adjacent to levee edges? and (2) Do native and alien species occupy different habitat types? We used our findings to address the broader question: do native and non-native species show habitat segregation, suggesting development of assemblage structure similar to that of co-evolved assemblages? Results indicate that habitat partitioning occurs among some clusters of species, but not all. Native Prickly Sculpin was found most often near riprapped levee edges, while alien Yellowfin Goby occupied adjacent muddy habitat, and the alien Shimofuri Goby showed no preference. Where two non-native species of caridean shrimp co-occurred, Siberian Prawn occupied unvegetated mud, while Oriental Grass Shrimp used primarily riprap. However, when only Siberian Prawn was present, it showed no preference for habitat type. Habitat associations changed slightly in response to seasonal shifts in habitat and spawning requirements. This study demonstrates that non-coevolved assemblages of organisms can develop resource partitioning to assist co-existence in novel habitats.

제주도 동부 먼바다 어장에서 겨울철에 어획된 저서생물의 분포특성

제주도 동부 먼바다 어장에서 겨울철에 어획된 저서생물의 분포특성

No evidence of increased demersal fish abundance six years after creation of marine protected areas along the southeast United States Atlantic coast

Marine protected areas (MPAs) have been used widely as a conservation and fisheries management tool to protect fish and habitats. We used a time series (2001–2014) of underwater videos from submersibles and remotely operated vehicles to determine whether a series of MPAs established in early 2009 along the southeast United States Atlantic coast has increased the number of fish species, density of fished species, or the density of Rhomboplites aurorubens (Cuvier, 1829) compared to adjacent, non-reserve areas. We used univariate and multivariate approaches at two spatial scales (region-wide and MPA-specific) to test for a change in the number or density of fish species inside compared to outside MPAs. Overall, 185 fish taxa were observed from 1021 video transects across all years of the study. We did not observe a higher number of species, density of fished species, or density of R. aurorubens inside compared to outside MPAs, either after region-wide standardization using generalized additive models or for nominal analyses focusing on two (Edisto or North Florida) MPAs. Using non-metric multidimensional scaling and analysis of similarity, we did not observe any change in community structure occurring inside the MPAs that was not simultaneously occurring outside the MPAs, both at the region-wide or MPA-level scale. We did not detect unique changes to the fish community inside MPAs after their creation, which could be due to low statistical power, not enough data post-MPA creation, low compliance rates, or suboptimal MPA shape and size, or some combination thereof. Given their current relatively low abundances, the sampling effort required to effectively assess potential MPA effects for most grouper species is well beyond current or historical levels of sampling.

New data on the longevity of coastal cod Gadus morhua Linnaeus, 1758 in the White Sea

The cod, Gadus morhua, is a common and abundant demersal fish in the White Sea coastal zone. The published data on the maximum age of White Sea cod still requires additional documentation, because some authors have noted difficulties in age determination by otoliths of large specimens. To obtain accurate data on the longevity of this species in the White Sea, an image analysis of thin-sections of otoliths was made for age estimation. Research surveys in the Chupa Inlet and adjacent waters of the Kandalaksha Bay were conducted in June to August from 2007 to 2013. The five largest specimens of a total of 3564 captured fish were selected for age determination. Age of these largest individuals ranged between 7 and 12 years, total length and weight varied from 60.2 to 77.0 cm and from 2.4 to 6.1 kg, respectively. According to the data, maximal White Sea cod longevity is greater than in previously published data, and demonstrates similar longevity to conspecifics from the Baltic and North seas, whereas its life cycle is much shorter than cod from the Northeast Arctic, Iceland, Greenland, Newfoundland and Labrador stocks.

Seasonal variation in species composition and abundance of demersal fish and invertebrates in a Seagrass Natural Reserve on the eastern coast of the Shandong Peninsula, China

Seagrass habitats are structurally complex ecosystems, which support high productivity and biodiversity. In temperate systems the density of seagrass may change seasonally, and this may influence the associated fish and invertebrate community. Little is known about the role of seagrass beds as possible nursery areas for fish and invertebrates in China. To study the functioning of a seagrass habitat in northern China, demersal fish and invertebrates were collected monthly using traps, from February 2009 to January 2010. The density, leaf length and biomass of the dominant seagrass Zostera marina and water temperature were also measured. The study was conducted in a Seagrass Natural Reserve (SNR) on the eastern coast of the Shandong Peninsula, China. A total of 22 fish species and five invertebrate species were recorded over the year. The dominant fish species were Synechogobius ommaturus, Sebastes schlegelii, Pholis fangi, Pagrus major and Hexagrammos otakii and these species accounted for 87% of the total number of fish. The dominant invertebrate species were Charybdis japonica and Octopus variabilis and these accounted for 98% of the total abundance of invertebrates. There was high temporal variation in species composition and abundance. The peak number of fish species occurred in August–October 2009, while the number of individual fish and biomass was highest during November 2009. Invertebrate numbers and biomass was highest in March, April, July and September 2009. Temporal changes in species abundance of fishes and invertebrates corresponded with changes in the shoot density and leaf length of the seagrass, Zostera marina.

中街山列岛海洋保护区鱼类物种多样性

The Zhongjieshan Islands Marine Protected Area( MPA) is located in the central area of the Zhoushan fishing ground. It lies to the east of Zhoushan Islands District in Zhejiang Province and is historically known as the "fish warehouse"of the East China Sea. Fish community taxonomy and eco-group data from eight bottom trawl surveys in Zhongjieshan Islands MPA,carried out from 2010 to 2012,were used to examine species composition in detail. Indices such as Margalef' s species richness index,Shannon-Wiener' s species diversity index,Pielou' s species evenness index,resource density index as well as Pinkas' s IRI were used to analyze the status of fish diversity in the protected area. A total of 55 fish species belonging to 2 classes,12 orders,32 families and 44 genera were collected during the survey. 26 species from the order Perciformes( accounting 47. 3% of the total species) and 41 reef species( 74. 5% of the total species) were captured. There were 30 warm temperate species,24 warm water species and 1 cold temperate species,and nearly 70% of total rare species were warm temperate species. There were 27 local species,24 offshore migrating species and 24 seasonal species. Forty percent of the fish caught were demersal,36. 4% were meso-demersal and 23. 6% were pelagic. The dominant species in each habitat layer was examined,Chaeturichthys stigmatias was the most abundant demersal fish,Harpodon nehereus was the most dominant meso-demersal fish. Fish in the family Engraulidae dominated the surface waters.The mean biomass index of the study area was highest in summer( 1043. 7 kg / km2) and lowest in spring. The abundance density index was highest in spring( 122×103ind / km2),but lowest in winter. Both the biomass index and the abundance density index in the highest season were significantly different from that in the lowest season( P 0. 05). The average Margalef's species richness index was highest in winter,but lowest in autumn,while the highest and lowest of both Shannon-Wiener's species diversity index and Pielou's species evenness index were in summer and autumn,respectively.Hierarchical clustering and further non-metric multidimensional scaling( NMDS) analysis indicated extremely significant seasonal changes in the fish community structure( P0. 01). The structure of fish resources in Zhongjieshan Islands MPA was significantly influenced by offshore seasonal migrating species,and the seasonal dynamic of fish distributions showed alternate migratory rhythm. Although the diversity of the protected area showed a downward trend,and the dominance of traditional economic species gradually declined or marginalized,the unique reef habitat still played an important role in both maintaining the local species and offering more bio-available habitat. With the development of marine ranching and implementation of a range of resource protection and restoration measures,the family Sciaenidae became a dominant group,and a large number of small forage fish appeared in the protected area.

The effects of submarine canyons and the oxygen minimum zone on deep-sea fish assemblages off Hawai'i

Submarine canyons are reported to be sites of enhanced fish biomass and productivity on continental margins. However, little is known about the effects of canyons on fish biodiversity, in particular on oceanic islands, which are imbedded in regions of low productivity. Using submersibles and high-definition video surveys, we investigated demersal fish assemblages in two submarine canyons and slope areas off the island of Moloka'i, Hawai'i, at depths ranging from 314 to 1100m. We addressed the interactions between the abundance, species richness and composition of the fish assemblage, and organic matter input and habitat heterogeneity, testing the hypotheses that heterogeneous bottom habitats and higher organic matter input in canyons enhance demersal fish abundance, and species density, richness and diversity, thereby driving differences in assemblage structure between canyons and slopes. Sediment type, substrate inclination, water-mass properties (temperature and dissolved oxygen) and organic matter input (modeled POC flux and percent detritus occurrence) were put into multivariate multiple regression models to identify potential drivers of fish assemblage structure. A total of 824 fish were recorded during ∼13h of video yielding 55 putative species. Macrouridae was the most diverse family with 13 species, followed by Congridae (5), Ophidiidae (4) and Halosauridae (3). Assemblage structure changed markedly with depth, with the most abrupt change in species composition occurring between the shallowest stratum (314–480m) and intermediate and deep strata (571–719m, 946–1100m). Chlorophthalmus sp. dominated the shallow stratum, macrourids and synaphobranchid eels at intermediate depths, and halosaurs in the deepest stratum. Assemblages only differed significantly between canyon and slope habitats for the shallow stratum, and the deep stratum at one site. Dissolved oxygen explained the greatest proportion of variance in the multivariate data, followed by POC flux and percent organic-detritus occurrence. Fish abundances were generally higher in canyons but only statistically significant for the deepest stratum. Reduced fish abundances both in canyon and slope transects occurred at intermediate depths within the core of the oxygen minimum zone (OMZ). Species density, diversity and richness and abundance were usually higher in the canyons, but only statistically higher in the deepest stratum. Possible causes for increased abundance and species densities and richness in the deepest stratum in canyons include reduced disturbance at deeper depths. We conclude that submarine canyons on oceanic islands are likely to be sites of enhanced fish abundance and species richness, but that these enhancing effects are offset when oxygen concentrations fall below ∼0.7mll−1 in OMZs.

Variability in behaviour of four fish species attracted to baited underwater cameras in the North Sea

Baited underwater camera (BUC) systems to estimate demersal fish abundance are becoming increasingly considered as an alternative to traditional survey methods, particularly in environments that contain sensitive habitats or protected species. Based on 27 replicate deployments of BUCs at 100 m depth in the northern North Sea, in rank order of abundance, hagfish (Myxine glutinosa), flatfish mainly dabs (Limanda limanda), whiting (Merlangius merlangus) and haddock (Melanogramusaeglefinus) were observed consistently at baits. Higher maximum numbers (Nmax) occurred during daytime in all species with the most significant effect in flatfish, 18 in daytime and 5 at night-time. Bottom current had no significant effect on numbers of whiting, flatfish or haddock. The Nmax of hagfish was strongly related to current speed in a non-linear way with an increase in numbers up to 10 cm s−1 and then decrease in Nmax at higher water speeds. Understanding and accounting for such species-specific influences is important in the design of long term monitoring surveys using baited cameras.

The first demersal trawl survey of benthic fish and invertebrates in the Beaufort Sea since the late 1970s

This study represents the first demersal trawl survey of marine fishes and invertebrates in offshore waters of the Beaufort Sea since 1977. Species composition, distribution, and abundance of demersal fish and benthic invertebrates were assessed with standard methods and demersal trawl gear by the Alaska Fisheries Science Center. Fishes made up 6% of the total catch weight, and invertebrates made up the remaining 94% of the catch weight. A total of 32 species of fish were identified, two taxa were identified to genus and one to family, and 174 taxa of invertebrates were identified. The most abundant demersal fishes were polar cod (Boreogadus saida), eelpouts (Lycodes spp.), Bering flounder (Hippoglossoides robustus), and walleye pollock (Theragra chalcogramma). The most abundant invertebrates were notched brittle stars (Ophiura sarsi), snow crab (Chionoecetes opilio), mussels (Musculus spp.), and the mudstar (Ctenodiscus crispatus). We documented or confirmed extension to the known ranges of four species of fishes: walleye pollock, Pacific cod (Gadus macrocephalus), festive snailfish (Liparis marmoratus), and eyeshade sculpin (Nautichthys pribilovius). We also documented the presence of commercial-sized snow crab (Chionoecetes opilio), which has not previously been recorded in the North American Arctic.

Annual, Seasonal, and Regional Variability in Diet of Atlantic Croaker (Micropogonias undulatus) in Chesapeake Bay

Atlantic croaker is one of the most abundant demersal fish in Chesapeake Bay. Until recently, when substantial declines in abundance have occurred, high biomass supported elevated fisheries landings. Therefore, study of the diet of Atlantic croaker is important to understand its own dynamics and its role in the Chesapeake Bay ecosystem. Patterns in the diet of croaker varied annually, seasonally, and spatially, but were not strongly correlated with any measured environmental variables. Although the majority of the diet of croaker consisted of polychaetes and other benthic items, about 20% of the croaker diet by weight consisted of anchovy and other fishes. Croaker consumption of anchovy is likely a result of crepuscular feeding that has not been captured in previous studies that sampled during the day and with bottom trawls. Thus, croaker influences both the benthic and pelagic components of the Chesapeake Bay food web and incorporating such diel patterns in diet may increase the reliability of fishery ecosystem models.

A review of the spatial extent of fishery effects and species vulnerability of the deep-sea demersal fish assemblage of the Porcupine Seabight, Northeast Atlantic Ocean (ICES Subarea VII)

Abstract Priede, I. G., Godbold, J. A., Niedzielski, T., Collins, M. A., Bailey, D. M., Gordon, J. D. M., and Zuur, A. F. 2011. A review of the spatial extent of fishery effects and species vulnerability of the deep-sea demersal fish assemblage of the Porcupine Seabight, Northeast Atlantic Ocean (ICES Subarea VII). – ICES Journal of Marine Science, 68: 281–289. We review information from scientific trawl surveys carried out between 1977 and 2002 in the Porcupine Seabight and Abyssal Plain area of the Northeast Atlantic (240–4865 m water depth). Since the late 1980s, commercial bottom-trawl fisheries targeting mainly roundnose grenadier (Coryphaenoides rupestris), black scabbardfish (Aphanopus carbo), and orange roughy (Hoplostethus atlanticus) have been operating at depths of 500–1500 m, intersecting the depth ranges of 77 demersal fish species that would therefore be vulnerable to fishery effects. Comparisons of trawls pre-1989 and post-1997 indicate a significant decrease in total abundance of demersal fish down to 2500 m. Detailed analyses of the 15 most-abundant species showed that nine species with depth ranges within the commercial fishing depth have decreased in abundance. Other species were either not affected (Bathypterois dubius) or only affected at the shallow end of their range (Coryphaenoides guentheri). Species with a minimum depth of occurrence &amp;gt;1500 m (Coryphaenoides armatus and Coryphaenoides leptolepis) increased in abundance over part of their depth range. Decreases in abundance are probably caused by commercial fishing activities, an effect that is transmitted downslope by removal of fish at the shallow end of their depth range, resulting in declines at the deeper end of the depth range. The estimated fishery area is ca. 52 000 km2, but the potential impact probably extends to ca. 142 000 km2 and to many non-target species.