scholarly journals Changes in the exploited demersal fish assemblages in the Southern Grand Banks (NAFO Divisions 3NO): 2002–2013

2014 ◽  
Vol 72 (3) ◽  
pp. 753-770 ◽  
Author(s):  
Adriana Nogueira ◽  
Xabier Paz ◽  
Diana González-Troncoso
Keyword(s):  
Fish Assemblages ◽  
Demersal Fish ◽  
Fishing Effort ◽  
Size Spectra ◽  
Grand Banks ◽  
Environmental Regimes ◽  
Commercial Species ◽  
Faunal Diversity ◽  
Different Levels ◽  
Population Rate

Abstract The Newfoundland Shelf supported one of the world’s greatest fisheries until the main commercial species collapsed more than two decades ago. We calculated three ecological indices for individual populations and five for community from the data obtained in the research surveys conducted by Spain in NAFO Regulatory Area Divisions 3NO between 2002 and 2013. We use data for 24 species to study the dynamics of major demersal fish assemblages (38–300, 301–600, and 601–1460 m depth) and evaluated how they have responded to different levels of exploitation. Trends and changes for individual populations (abundance and biomass, intrinsic population rate of growth, and mean length) and for all the community (ABC curves, indices of faunal diversity, proportion of non-commercial species, mean length in community and size spectra) were used to test ecological trends. Indices showed no homogeneous status and responded to different exploitation patterns, management, and environmental regimes in each assemblage. Our results show an improvement in the shallower and deeper assemblages and that fishing effort does not explain differences among each assemblage.

scholarly journals Demersal Fish Assemblages in NE Atlantic Seagrass and Kelp

Diversity ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 366
Author(s):  
Evie Furness ◽  
Richard K.F. Unsworth
Keyword(s):  
Species Richness ◽  
Fish Assemblages ◽  
Demersal Fish ◽  
Kelp Forests ◽  
Evidence Based ◽  
Ecological Value ◽  
Commercial Fish ◽  
Seagrass Meadows ◽  
The North ◽  
Commercial Species

Global fisheries are in decline, calling for urgent evidence-based action. One such action is the identification and protection of fishery-associated habitats such as seagrass meadows and kelp forests, both of which have suffered long-term loss and degradation in the North Atlantic region. Direct comparisons of the value of seagrass and kelp in supporting demersal fish assemblages are largely absent from the literature. Here, we address this knowledge gap. Demersal fish were sampled using a baited camera to test for differences between habitats in (1) the species composition of the fish assemblages, (2) the total abundance and species richness of fishes, and (3) the abundances of major commercial species. Seagrass and kelp-associated fish assemblages formed two significantly distinct groupings, which were driven by increased whiting (Merlangius merlangus) and dogfish (Scyliorhinus canicula) presence in seagrass and higher abundances of pollock (Pollachius pollachius) and goby (Gobiusculus flavescens) in kelp. The abundance, diversity, and species richness did not change significantly between the two habitats. We conclude that seagrass and kelp do support unique demersal fish assemblages, providing evidence that they have different ecological value through their differing support of commercial fish species. Thus, this study improves the foundation for evidence-based policy changes.

scholarly journals The structure of demersal fish assemblages in a cold, highly stratified environment

2011 ◽  
Vol 68 (9) ◽  
pp. 1896-1908 ◽  
Author(s):  
P-M. Chouinard ◽  
J-D. Dutil
Keyword(s):  
Environmental Conditions ◽  
Fish Assemblages ◽  
Species Abundance ◽  
Demersal Fish ◽  
Strong Correlations ◽  
Commercial Species ◽  
Identification Of Species ◽  
Detrended Canonical Correspondence Analysis ◽  
Potential Interactions ◽  
Trawl Surveys

Abstract Chouinard, P-M., and Dutil, J-D. 2011. The structure of demersal fish assemblages in a cold, highly stratified environment. – ICES Journal of Marine Science, 68: 1896–1908. Fish are a major component of marine ecosystems, with many species co-occuring in the same habitats. Potential interactions among species and with the environment can be studied through the identification of species assemblages. Data from bottom trawl surveys (2004–2008) conducted in the estuary and northern Gulf of St Lawrence were analysed using multivariate methods (cluster, multidimensional scaling, and detrended canonical correspondence analysis) to describe the structure and composition of demersal fish assemblages, including rare and smaller non-commercial species. The spatial variability in environmental conditions that characterizes the study area has a significant impact on the composition of fish assemblages in the region. In all, 35 taxa were classified as key, and 6 main fish assemblages were described, based on catch in numbers. These assemblages had a coherent spatial distribution in the study area, associated with either depth, salinity and temperature, or dissolved oxygen. The analyses showed overall strong correlations between species abundance and prevalent environmental conditions and explained 18.4% of the variance in species abundance data and 79.2% of the variance in the species–environment relationship.

scholarly journals Nonstationary Responses of Demersal Fishes to Environmental Variations in Temperate Waters of the Northwestern North Pacific under a Changing Climate

Fishes ◽  
2021 ◽  
Vol 6 (3) ◽  
pp. 22
Author(s):  
Qingsong He ◽  
Shuyang Ma ◽  
Qinwang Xing ◽  
Wenchao Zhang ◽  
Haiqing Yu ◽  
...  
Keyword(s):  
North Pacific ◽  
Negative Relationship ◽  
Demersal Fish ◽  
Fishing Effort ◽  
Asian Winter Monsoon ◽  
Changing Climate ◽  
Sst Variability ◽  
Environmental Variations ◽  
The Impact ◽  
Demersal Fishes

Although nonstationarity in marine ecosystems has attracted great attention, the nonstationary responses of demersal fishes to environmental variations induced by the changing climate are still not well understood. Here, we collected 21 time series of demersal fishes from 1956 to 2015 to investigate the climate-induced nonstationary responses in temperate waters of the northwestern North Pacific (NWP). We showed that these demersal fishes experienced state shifts in approximately 1986/87, accompanied by abrupt warming over this region. Moreover, the relationships between demersal fishes and sea surface temperature (SST) were found to change between the two identified eras (i.e., a weak relationship before 1986 and a strong negative relationship after 1986), which may be primarily caused by the alternating dominance of the East Asian winter monsoon and mega-ENSO on SST in temperate waters of the NWP. The identified climate-induced nonstationary responses of demersal fishes to SST variability in this study may provide implications for understanding climate-induced biological dynamics, predicting demersal fish fluctuations, coping with potential ecological risks, and the sustainable exploitation of fishery resources in the future climate. Note that the impact of fishing on the demersal fishes in temperate waters of the NWP was not assessed in this study due to the lack of fishing effort data and therefore the conclusions of our research should be approached with caution.

Demersal fish assemblages on seamounts exploited by fishing in the Azores (NE Atlantic)

2020 ◽  
Author(s):  
Régis Santos ◽  
Wendell Medeiros‐Leal ◽  
Ana Novoa‐Pabon ◽  
Hélder Silva ◽  
Mário Pinho
Keyword(s):  
Fish Assemblages ◽  
Demersal Fish ◽  
Ne Atlantic

Demersal fish biomass size spectra on the Scotian Shelf, Canada: species replacement at the shelfwide scale

1997 ◽  
Vol 54 (8) ◽  
pp. 1725-1735 ◽  
Author(s):  
D E Duplisea ◽  
S R Kerr ◽  
L M Dickie
Keyword(s):  
Time Series ◽  
Body Weight ◽  
Energy Input ◽  
Demersal Fish ◽  
Species Group ◽  
Total Biomass ◽  
Species Replacement ◽  
Scotian Shelf ◽  
Size Spectra ◽  
Species Groups

Three parameters were derived from annual biomass size spectra constructed for a 22-year time series of demersal fish data for the entire Scotian Shelf: (i) total sampled biomass density, (ii) modal body weight, and (iii) the shape of the various biomass size spectra. Temporal variability of these parameters was compared among six species groups and between the species groups and their total. Species-group biomass varied more over the time series than did the total biomass, indicating the presence of a system factor. Conversely, modal body weight was as variable, and sometimes more variable, for the total than it was within species groups, indicating variability mainly at the species level. The shape of the biomass size spectrum showed annual differences in variability owing mainly to contributions of species groups. This variability was higher than variability in the combined species totals. We conclude that total biomass is limited at the combined species (systemwide) level because it depends on energy input to the system. Variability is greater at the species group (subsystem) level because the multiage species-group biomasses do not equally reflect a given energy limitation. Neither modal body weight nor the shape of the biomass spectrum is sensitive to the degree of taxonomic aggregation, suggesting that both measures are independent of energy input (primary production). We found no evidence of consistent species replacement trends on the shelfwide scale and conclude that diffuse replacement best describes species succession on the Scotian Shelf as a whole.

Using an individual-based model of fish assemblages to study the response of size spectra to changes in fishing

2004 ◽  
Vol 61 (3) ◽  
pp. 414-431 ◽  
Author(s):  
Yunne-Jai Shin ◽  
Philippe Cury
Keyword(s):  
Fish Assemblages ◽  
Prey Availability ◽  
Empirical Studies ◽  
Marine Ecosystem ◽  
Predatory Fish ◽  
Size Spectrum ◽  
Individual Based Model ◽  
Size Spectra ◽  
Predation Mortality ◽  
Body Shapes

For most fish species, strong environmental constraints imposed by living in an aquatic medium have produced converging streamlined body forms without prehensile appendices. This similarity in body shapes highlights a common predation constraint: a predatory fish must have a jaw large enough to swallow its prey. Fish diets may then reflect local prey availability and predator–prey size ratios. Based on this size-based opportunistic predation process, the multispecies individual-based model OSMOSE (Object-oriented Simulator of Marine ecOSystem Exploitation) is used to investigate to what extent the size distribution of fish communities can contribute to better our understanding of the functioning of marine food webs and the ecosystem effects of fishing. Strong similarity in shape is found between simulated size spectra and those described in empirical studies. The existence of a curvature towards small size classes is discussed in the light of the size-based predation hypothesis, which implies that smaller fish may undergo higher predation mortality. Applying linear and quadratic regressions to the simulated size spectra allows the detection of variations in fishing pressure and the proposal of different ways to quantify them. In particular, it is shown that the slope of the size spectrum decreases quasilinearly with fishing mortality and that the curvature could help to detect ecosystem overexploitation.

scholarly journals Demersal fish assemblages and habitat characteristics on the continental shelf and upper slope of the north-western Mediterranean

2000 ◽  
Vol 80 (6) ◽  
pp. 981-988 ◽  
Author(s):  
Montserrat Demestre ◽  
Pilar Sánchez ◽  
Pere Abelló
Keyword(s):  
Continental Shelf ◽  
Fish Species ◽  
Fish Assemblages ◽  
Demersal Fish ◽  
Western Mediterranean ◽  
Habitat Characteristics ◽  
Species Assemblages ◽  
The North ◽  
Benthic Sediments ◽  
Upper Slope

Continental shelf and upper slope fish communities were studied along the Catalan coast based on 66 experimental bottom otter trawls. A total of 79 demersal fish species were studied by means of cluster analysis and multi-dimensional scaling (MDS) ordination for community structure. Analysis revealed the existence of five major location clusters. Similarity percentage analysis (SIMPER) was determined by comparing the dissimilarity between two groups of samples using the discriminating species. Geomorphological characteristics, bottom substratum and depth showed direct influences on species assemblages. High correlation between the biotic data samples and depth was observed. The fish species assemblages identified five main demersal fish associations which corresponded with the five location clusters and with five benthic sediments (mud of the upper slope, sand and gravel, mud of the shelf, muddy-sand and sand with rocky outcrops).

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