Changes in the Diet of Demersal Fish due to Eutrophication-Induced Hypoxia in the Kattegat, Sweden

1994 ◽  
Vol 51 (2) ◽  
pp. 321-336 ◽  
Author(s):  
Leif Pihl
Keyword(s):  
Fish Species ◽  
Gadus Morhua ◽  
Prey Species ◽  
Atlantic Cod ◽  
Benthic Communities ◽  
Demersal Fish ◽  
Organic Enrichment ◽  
Fish Diet ◽  
Dietary Shift ◽  
Term Change

The diets of five dominant bottom-feeding fish species, Atlantic cod (Gadus morhua), whiting (Merlangius merlangus), plaice (Pleuronectes platessa), dab (Limanda limanda), and American plaice (Hippoglossoides platessoides), were analysed during spring and autumn between May 1984 and April 1988 in the southeast Kattegat. A general long-term change in the diet of bottom-feeding fish in the Kattegat has taken place since the beginning of the century and, for some of the species, the feeding pattern was different from that in adjacent areas. The observed dietary shift appeared to be due to changes in species composition of benthic macrofauna. Prey species favored by increased organic enrichment were dominant in the diet. Several infaunal species increased in dietary importance during recent hypoxia. In contrast, during hypoxia, a reduction of epibenthic crustaceans was observed in the fish diet. This study emphasizes the potential effects of organic enrichment and hypoxia (due to eutrophication) on trophic interactions in marine benthic communities. Repeated stress from hypoxia might favor small-sized prey species with a short life cycle, which would in turn favor small-sized fishes. Thus, altered food resources and the direct effects of hypoxia might result in shift in dominance among demersal fish species.

scholarly journals Fish aggregating sound technique (FAST): how low-frequency sound could be used in fishing and ranching of cod

2018 ◽  
Vol 75 (4) ◽  
pp. 1258-1268 ◽  
Author(s):  
Björn Björnsson
Keyword(s):  
Fish Species ◽  
Gadus Morhua ◽  
Greenhouse Gas Emission ◽  
Atlantic Cod ◽  
Benthic Communities ◽  
Low Frequency ◽  
Wild Fish ◽  
Sea Cage ◽  
Free Ranging ◽  
Harmful Effects

Abstract In marine fisheries, considerable development has occurred in capture technology. Yet, some of the current fishing methods impact the environment by large greenhouse gas emission, harmful effects to benthic communities, and/or high bycatch of juvenile and unwanted species. It is proposed that for some fish species these deficiencies could be mitigated by classical conditioning using sound and food reward to concentrate wild fish before capture with environmentally friendly fishing gear. Atlantic cod (Gadus morhua), which globally is among the fish species with the highest landed value, can be acoustically trained. In a sea cage, it takes about a week to train a group of naïve cod to associate low frequency (250 Hz) sound with food, whereas the training of a group of naïve cod accompanied with one trained cod takes less than a day. In inshore areas, it takes a few weeks to attract thousands of cod to stations where food is regularly delivered. These conditioned cod wait at the stations for their meals and do not mingle much with the unconditioned cod which hunt for wild prey. It is suggested that by calling acoustically conditioned fish between stations, a much larger number of naïve fish can be gathered. This so-called fish aggregating sound technique (FAST) may thus facilitate the accumulation of wild fish and expedite their capture with a purse seine or a trap in a way that minimizes fuel consumption and mortality of juveniles and unwanted species. The operation of FAST requires exclusive rights of a designated fishing area. The exclusivity makes it possible to on-grow the fish in free-ranging schools and sea cages for several months to increase their size and food quality before capture.

scholarly journals Legacy and Emerging Contaminants in Demersal Fish Species from Southern Norway and Implications for Food Safety

Foods ◽  
2020 ◽  
Vol 9 (8) ◽  
pp. 1108
Author(s):  
Marco Parolini ◽  
Sara Panseri ◽  
Federico Håland Gaeta ◽  
Federica Ceriani ◽  
Beatrice De Felice ◽  
...  
Keyword(s):  
Food Safety ◽  
Fish Species ◽  
Gadus Morhua ◽  
Emerging Contaminants ◽  
Atlantic Cod ◽  
Demersal Fish ◽  
Polycyclic Aromatic ◽  
Low Levels ◽  
Southern Norway ◽  
Number Of Individuals

The present study aimed at measuring the levels of legacy and emerging contaminants in fillet samples from four demersal fish caught in two fishing sites from Southern Norway, in order to assess possible implications for food safety. Levels of organochlorine compounds (OCs), organophosphate pesticides (OPs), polychlorinated biphenyls (PCBs), polybromodiphenyl ethers (PBDE), per- and polyfluoroalkyl substances (PFASs), and polycyclic aromatic hydrocarbons (PAHs) were measured in fillet from Atlantic cod (Gadus morhua), European plaice (Pleuronectes platessa), lemon sole (Microstomus kitt), and European flounder (Platichthys flesus) specimens. A negligible contamination by all the investigated chemicals was noted in both the fishing sites, as very low levels of OCs, PCBs, and PFASs were noted in a limited number of individuals for each species. Considering the levels of contaminants measured in fillets of the four demersal fish species, negligible risk for human health for Norwegian consumers can be supposed.

Transition to an alternate state in a continental shelf ecosystem

2004 ◽  
Vol 61 (4) ◽  
pp. 505-510 ◽  
Author(s):  
Jae S Choi ◽  
Kenneth T Frank ◽  
William C Leggett ◽  
Ken Drinkwater
Keyword(s):  
Fish Species ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Demersal Fish ◽  
Commercial Fishing ◽  
Progressive Decline ◽  
Ecological Changes ◽  
Decadal Scale ◽  
Flow Through

The collapse of Atlantic cod (Gadus morhua) stocks in the northwest Atlantic Ocean ranks among the most dramatic and widely known ecological changes of the 20th century. Less widely known are the systemic changes that occurred within these areas prior to and coincident with the cod collapse. Our analysis of a fishery-independent, long-term, standardized database collected on the eastern Scotian Shelf off Nova Scotia revealed that during the past four decades, coherent, community-level reductions in body size, biomass, and physiological condition have occurred in the resident demersal fish species. The changes occurred over large spatial (>104 km2) and short temporal (<10 years) scales, suggesting a progressive decline in the nature and extent of the energy flow through the benthic system. The unexpected and persistent poor condition of a variety of morphologically and functionally dissimilar demersal fish species, living in an environment of reduced intra- and inter-specific competition, suggests a decoupling of the benthic– pelagic systems. This decoupling appears to be attributable to a cascading series of processes involving the cumulative removal of biomass resulting from commercial fishing, compensatory and self-stabilizing increases in pelagic fish biomass, and a decline in groundfish productivity exacerbated by decadal scale variability in water temperature and stratification.

Parasites as biological tags in population studies of marine organisms: an update

Parasitology ◽  
2002 ◽  
Vol 124 (7) ◽  
pp. 153-163 ◽  
Author(s):  
K. MACKENZIE
Keyword(s):  
Population Biology ◽  
Gadus Morhua ◽  
Population Studies ◽  
Marine Invertebrates ◽  
Atlantic Cod ◽  
Demersal Fish ◽  
Ecological Groups ◽  
Multidisciplinary Study ◽  
Fish Hosts ◽  
Biological Tags

This paper reviews the work published over the past decade on the use of parasites as biological tags in population studies of marine fish, mammals and invertebrates. Fish hosts are considered in taxonomic and ecological groups as follows: demersal, anadromous, small pelagic, large pelagic and elasmobranch. Most studies were carried out on demersal fish, particularly on members of the genera Merluccius (hake), Sebastes (rockfish) and on Atlantic cod Gadus morhua L., but Pacific salmonids and small pelagic fish of the genus Trachurus are also well-represented. A current multidisciplinary study of the population biology of horse mackerel Trachurus trachurus in European waters, which includes the use of parasites as tags, is described. Two studies recognize the potential for using parasites as tags for cetaceans but, in spite of the considerable potential for this approach in population studies of elasmobranchs, no original study has been carried out on this group for over ten years. Studies of parasites as tags for marine invertebrates have concentrated on squid. Recent trends in the use of parasites as biological tags for marine hosts are discussed.

scholarly journals The acoustic dead zone: theoretical vs. empirical estimates, and its effect on density measurements of semi-demersal fish

2009 ◽  
Vol 66 (6) ◽  
pp. 1364-1369 ◽  
Author(s):  
L. G. S. Mello ◽  
G. A. Rose
Keyword(s):  
Newfoundland And Labrador ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Dead Zone ◽  
Demersal Fish ◽  
Depth Gradient ◽  
Density Measurements ◽  
Acoustic Data ◽  
Empirical Estimates ◽  
The Difference

Abstract Mello, L. G. S., and Rose, G. A. 2009. The acoustic dead zone: theoretical vs. empirical estimates, and its effect on density measurements of semi-demersal fish. – ICES Journal of Marine Science, 66: 1364–1369. The height of the acoustic dead zone, the region near the seabed where fish cannot be resolved acoustically, was calculated both theoretically (DZt) and empirically (DZe). The DZe was based on measurements of depth and trawl geometry from sensors (SCANMAR) mounted on a bottom trawl deployed during a survey off Newfoundland and Labrador in winter 2007. Acoustic data were acquired while trawling, using a 38-kHz echosounder (Simrad EK500) with a hull-mounted transducer. The DZe was calculated as the difference between the trawl-footrope depth and the corresponding acoustically sensed, seabed depth. EK500 and SCANMAR estimates of seabed depth were significantly different. The fish caught were mostly Atlantic cod (Gadus morhua). The estimates of DZe ranged between 2.0 and 3.5 m and were greater than DZt by 0.1–0.9 m in more than half the cases. Three values of acoustically derived cod densities were estimated for each tow, without dead-zone correction and with corrections for DZt and DZe. When compared with DZt corrections, DZe resulted in negative (6–12%) and positive (9–35%) corrections to cod density. A general linear model revealed that the seabed depth gradient, standard deviation of estimated fish density in the dead zone, and wind direction and force explained 85% of the difference between DZt and DZe estimates. These factors affected the detection of the seabed and biased acoustically derived indices of demersal-fish abundance.

scholarly journals Animal Welfare Issues in Capture-Based Aquaculture

Animals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 956
Author(s):  
Uthpala Chandararathna ◽  
Martin Hugo Iversen ◽  
Kjetil Korsnes ◽  
Mette Sørensen ◽  
Ioannis N. Vatsos
Keyword(s):  
Fish Species ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Farming Systems ◽  
Recovery Phase ◽  
Market Size ◽  
Fish Welfare ◽  
Intensive Farming ◽  
Intensive Aquaculture ◽  
Aquaculture Production

Capture-based aquaculture (CBA) represents a type of intensive aquaculture production system for some economically valuable fish species, such as bluefin tuna (Thunnus thynnus), eel (Anguilla spp.) and Atlantic cod (Gadus morhua). In CBA, fish are captured from the wild in certain periods of the year, and following a recovery phase, they are kept in rearing facilities for a period of time, until they reach the market size. In this case, the fish are wild and have not gone through domestication like other fish species that are reproduced and farmed under the established farming systems. Therefore, these fish are not genetically adapted to live under the intensive farming conditions, and thus their welfare may be compromised in different manners compared to their domesticated counterparts. This review presents an overview of the current situation of CBA, while focusing on the assessment of fish welfare in CBA. The most commonly used fish welfare indicators will be discussed in relation to the different stages of CBA.

scholarly journals Low incidence of plastic ingestion among three fish species significant for human consumption on the island of Newfoundland, Canada

2019 ◽  
Author(s):  
Max Liboiron
Keyword(s):  
Atlantic Salmon ◽  
Fish Species ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Human Consumption ◽  
Cultural Importance ◽  
Capelin Mallotus Villosus ◽  
Food Fish ◽  
Low Incidence ◽  
Contamination Levels

This study reports the first baselines of plastic ingestion for three fish species that are common commercial and sustenance food fish in Newfoundland. Species collections occurred between 2015 and 2016 for Atlantic cod (Gadus morhua), Atlantic salmon (Salmo salar), and capelin (Mallotus villosus). The frequency of occurrence (%FO) of plastic ingestion for both Atlantic salmon (n = 69) and capelin (n = 350) was 0%. Of the 1010 Atlantic cod individuals collected over two years, 17 individuals had ingested plastics, a %FO of 1.68%. This is the only multi-year investigation of plastic ingestion in Atlantic cod for the Northwest Atlantic, and the first baseline of plastic ingestion in Atlantic salmon and capelin on the island of Newfoundland. Considering the ecological, economic, and cultural importance of these fish species, this study is the beginning of a longitudinal study of plastic ingestion to detect any future changes in contamination levels.

scholarly journals Diets of the Barents Sea cod (<i>Gadus morhua</i>) from the 1930s to 2018

2021 ◽  
Vol 13 (3) ◽  
pp. 1361-1370
Author(s):  
Bryony L. Townhill ◽  
Rebecca E. Holt ◽  
Bjarte Bogstad ◽  
Joël M. Durant ◽  
John K. Pinnegar ◽  
...  
Keyword(s):  
Gadus Morhua ◽  
Visual Analysis ◽  
Barents Sea ◽  
Atlantic Cod ◽  
Fish Diet ◽  
The North ◽  
The United Kingdom ◽  
Federal Research ◽  
The Barents Sea ◽  
The Uk

Abstract. A new dataset on the diet of Atlantic cod in the Barents Sea from the 1930s to the present day has been compiled to produce one of the largest fish diet datasets available globally. Atlantic cod is one of the most ecologically and commercially important fish species in the North Atlantic. The stock in the Barents Sea is by far the largest, as a result of both successful management and favourable environmental conditions since the early 2000s. As a top predator, cod plays a key role in the Barents Sea ecosystem. The species has a broad diet consisting mainly of crustaceans and teleost fish, and both the amount and type of prey vary in space and time. The data – from Russia, Norway and the United Kingdom – represent quantitative stomach content records from more than 400 000 fish and qualitative data from 2.5 million fish. Many of the data are from joint collaborative surveys between Norway and Russia. The sampling was conducted throughout each year, allowing for seasonal, annual and decadal comparisons to be made. Visual analysis shows cod diets have changed considerably from the start of the dataset in the 1930s to the present day. There was a large proportion of herring in the diets in the 1930s, whereas in more recent decades capelin, invertebrates and other fish dominate. There are also significant interannual asynchronous fluctuations in prey, particularly capelin and euphausiids. Combining these datasets can help us understand how the environment and ecosystems are responding to climatic changes, and what influences the diet and prey switching of cod. Trends in temperature and variability indices can be tested against the occurrence of different prey items, and the effects of fishing pressure on cod and prey stocks on diet composition could be investigated. The dataset will also enable us to improve parametrization of food web models and to forecast how Barents Sea fisheries may respond in the future to management and to climate change. The Russian data are available through joint projects with the Polar Branch of the Russian Federal Research Institute of Fisheries and Oceanography (VNIRO). The UK and Norwegian data (Townhill et al., 2020) are being released with this paper at https://doi.org/10.21335/NMDC-2139169383.

Is Juvenile Natural Mortality in Marine Demersal Fish Variable?

1993 ◽  
Vol 50 (8) ◽  
pp. 1591-1598 ◽  
Author(s):  
Ransom A. Myers ◽  
Noel G. Cadigan
Keyword(s):  
Interannual Variability ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Demersal Fish ◽  
Independent Component ◽  
Melanogrammus Aeglefinus ◽  
Natural Mortality ◽  
Juvenile Mortality ◽  
Merlangius Merlangus ◽  
Haddock Melanogrammus Aeglefinus

We test the hypothesis that the interannual variability of the density-independent component of juvenile natural mortality is a major source of variability in abundance of marine demersal fish. Our tests use data on populations for which there are research surveys consisting of two simultaneous estimates of abundance of young juveniles soon after settlement and two more simultaneous estimates of the same cohort a year later. We applied our test to 14 populations of Atlantic cod (Gadus morhua), haddock (Melanogrammus aeglefinus), whiting (Merlangius merlangus), plaice (Pleuronectes platessa), and sole (Solea vulgaris). We conclude that, in all populations examined except North Sea sole, there was very little or no interannual variability in the density-independent component of juvenile mortality.

Sea fish fraud? A confirmation of Gadoid species food labelling

2017 ◽  
Vol 119 (1) ◽  
pp. 122-130 ◽  
Author(s):  
Veronika Kyrova ◽  
Pavla Surmanova ◽  
Vladimir Ostry ◽  
Irena Rehurkova ◽  
Jiri Ruprich ◽  
...  
Keyword(s):  
Fish Species ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Accurate Identification ◽  
Content Type ◽  
Fish Meat ◽  
Fish Fillets ◽  
Quality Of Food ◽  
Sea Fish

Purpose Gadoid fish and hake are the species of fishes most frequently imported to the Czech Republic. The purpose of this paper, cross-country hygiene study, is to determine sea fish fraud labelling on the Czech market and catering. Design/methodology/approach In total, 57 samples of commercial Gadoid fish product from different manufacturers, distributors and catering facilities were gathered. Gadidae family, hake (Merluccius spp. Raf.), saithe (Pollachius virens L.), Atlantic cod (Gadus morhua L.), Alaska pollock (Theragra chalcogramma Pall.), were detected in fish meat, fish products and fish meals by the qualitative PCR method. Findings In total, 47 samples were labelled as a Gadoid fish, which were confirmed in 43 cases. Six samples were labelled as a hake and were confirmed in five samples. Four samples were labelled as a fish fillets. Three samples of fish fillets were identified as a hake and one sample was detected as a mixture of Alaska pollock and Atlantic cod. Social implications In recent years, due to increasing interest from consumers in the sea fish meat market, accurate Identification of fish species has become more important. The mislabelling of sea fish species, whether intentional or not, was on observed on the Czech market and in catering facilities. Economic factors influence the accuracy of labelling of fish meat, which is a concern as mislabelling can threaten public health. Originality/value The study was concentrated on the monitoring of hygiene and quality of food products and catering facilities. This study provides greater awareness of the condition and quality of food on the market and to the extent of fraudulent practices amongst dealers and producers.

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