Demersal Fish Assemblages on the Scotian Shelf, Northwest Atlantic: Spatial Distribution and Persistence

1989 ◽  
Vol 46 (S1) ◽  
pp. s134-s152 ◽  
Author(s):  
Robin Mahon ◽  
Robert W. Smith
Keyword(s):  
Environmental Variables ◽  
Fishery Management ◽  
Fish Assemblages ◽  
Environmental Gradients ◽  
Demersal Fish ◽  
Assemblage Structure ◽  
Bay Of Fundy ◽  
Scotian Shelf ◽  
Species Groups ◽  
Temporal And Spatial

This study is based on 18 surveys, 12 in summer, and three each in spring and fall, with bottom trawls over the Scotian Shelf and Bay of Fundy. The data analysis sequence was: temporal and spatial aggregation of trawl sets; estimation of interspecies and intersite distance indices; clustering and ordination of sites and species, and discrimination of site groups using environmental variables. Nine species-groups, and 10 site-groups were defined, and displayed in a two-way table. Depth and temperature were the environmental variables most strongly associated with differences in assemblage structure among site-groups. Changes in assemblage structure from one area to another were distinct but apparently gradual, with no sharp assemblage boundaries. This pattern is expected if species are distributed independently on environmental gradients, rather than if assemblages consist of highly co-evolved, interdependent species. The observed spatial patterns were highly persistent through time. There are regions which are relatively homogeneous with regard to species composition and which can therefore be useful in dealing with bycatch problems. However, this study does not indicate the existence of discrete assemblages which might be appropriate as ecologically based fishery management units.

Among- and within-tributary responses of riverine fish assemblages to habitat featuresContribution of the Group for Interuniversity Research in Limnology (GRIL). We dedicate this paper to the memory of our colleague Réjean Fortin.

2008 ◽  
Vol 65 (7) ◽  
pp. 1379-1393 ◽  
Author(s):  
Yorick Reyjol ◽  
Marco A. Rodríguez ◽  
Nathalie Dubuc ◽  
Pierre Magnan ◽  
Réjean Fortin
Keyword(s):  
Environmental Variables ◽  
Fish Assemblages ◽  
Environmental Gradients ◽  
Assemblage Structure ◽  
Foraging Efficiency ◽  
Habitat Features ◽  
Ottawa River ◽  
Mixed Regression ◽  
Riverine Fish ◽  
Predictable Variation

We quantified fish abundance and environmental variables at 170 sites distributed among 11 tributaries of the Ottawa River, Quebec, Canada, to assess the relative importance of among- and within-tributary variation in riverine fish assemblages. Additionally, we determined (i) which environmental variables were most strongly associated with each type of variation and (ii) whether ecomorphological traits in fish assemblages were predictably related to environmental gradients. Partitioning of variation by means of partial ordination indicated that assemblages were less variable among (38.7% of the total variation) than within (61.3%) tributaries. Water transparency singly accounted for 33.3% of the variation among tributaries, whereas macrophyte cover and river width jointly accounted for 8.3% of the variation within tributaries. These results suggests that differences in habitat features among tributaries may account for a substantial fraction of the predictable variation in assemblage structure at the watershed scale, an aspect not emphasized in previous studies of riverine fish assemblages. Mixed regression analyses relating ecomorphological traits to environmental variables showed that the environmental variables most strongly associated with assemblage structure were significantly related to traits associated with predator avoidance or foraging efficiency.

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.

scholarly journals Stability of the relationships among demersal fish assemblages and environmental-trawling drivers at large spatio-temporal scales in the northern Mediterranean Sea

2020 ◽  
Vol 83 (S1) ◽  
pp. 153
Author(s):  
Bastien Mérigot ◽  
Jean Claude Gaertner ◽  
Anik Brind’Amour ◽  
Pierluigi Carbonara ◽  
Antonio Esteban ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Environmental Changes ◽  
Fish Assemblages ◽  
Environmental Gradients ◽  
Temporal Stability ◽  
Demersal Fish ◽  
Minor Role ◽  
Carbon Biomass ◽  
Spatio Temporal ◽  
A Minor

Trawling pressure and environmental changes may affect the composition of fish assemblages. Our knowledge on large spatio-temporal patterns of demersal fish composition remains incomplete for the Mediterranean Sea. We investigated (1) the spatio-temporal stability of demersal assemblages, (2) the relationships between these assemblages and potential structuring factors (trawling pressure and environmental conditions) in order to assess the dynamic of the assemblage structure at the scale of the northern Mediterranean Sea. We analysed a dataset of 18062 hauls from 10 to 800 m depth performed annually during the last two decades across 17 Geographical Sub-Areas (GSAs) (MEDITS program). A multi-table analysis (STATICO-CoA) evidenced a strong inter-GSAs stability in the organization of assemblages, with specificities for some GSAs. The most stable structuring factors were linked to combined gradients of chlorophyll a, phytoplancton carbon biomass and temperature, inversely correlated with depth, salinity and nutrient gradients (axis 1 of the STATICO-CoA compromise, 93.74% of the total variability). A common pattern linking the distribution of species to these environmental gradients was evidenced for most of the 17 GSAs. Estimate of trawling pressure showed a minor role in the organization of the assemblages for the spatial scale and years investigated (axis 2, 4.67%).

scholarly journals Correlations Between Fish Assemblage Structure and Environmental Variables of Taruwa Pond in Nawalparasi District, Province No. 4, Nepal

2021 ◽  
Vol 11 (1) ◽  
pp. 1-8
Author(s):  
JASH HANG LIMBU ◽  
KESHI CHAUDHARY
Keyword(s):  
Temporal Variation ◽  
Fish Assemblage ◽  
Environmental Variables ◽  
Fish Assemblages ◽  
Mesh Size ◽  
Assemblage Structure ◽  
Fish Assemblage Structure ◽  
Fish Community Structure ◽  
Water Parameters ◽  
Analysis Of Similarity

The correlations between fisheries diversity and environmental variables of Nepal’s Pond are poorly understood. This study aims to investigate temporal variation of fish assemblage at Taruwa Pond in Nawalparasi district, Province no. 4, Nepal from October 2018 to April 2019. For the fish agglomeration, cast net of 4 kg in weight and 3.80 m in length and 22.5 m breadth with 12 mm mesh size was used. In total, 579 individuals representing 16 fish species, 10 families, and 12 genera were recorded. According to similarity percentage analysis, the most contributory species were Puntius ticto (27.92%) followed by Danio devario (12.06%), Puntius terio (9.76%), Badis badis (7.31%), Lepidocephalichthys guntea (5.57%) and Puntius sophore (5.57%). Analysis of similarity suggested that fish community structure was significantly different in temporal variation (R = 0.321, p<0.01). Based on the cluster analysis, fish assemblages were isolated into two distinct groups at Bray-curtis similarity. The Canonical Correspondence Analysis distinctly indicated that the water parameters of dissolved oxygen, carbon-dioxide, depth, and water temperature play an important role in influencing the fish assemblage structure of Taruwa Pond.

scholarly journals Composition and assemblage structure of demersal fish from São Cristóvão beach, Areia Branca, RN

2012 ◽  
Vol 12 (3) ◽  
pp. 108-117 ◽  
Author(s):  
Natália Carla Fernandes de Medeiros Dantas ◽  
Caroline Vieira Feitosa ◽  
Maria Elisabeth de Araújo
Keyword(s):  
Sandy Beach ◽  
Fish Assemblages ◽  
General Pattern ◽  
Fish Fauna ◽  
Demersal Fish ◽  
Sandy Beaches ◽  
Assemblage Structure ◽  
Northeastern Brazil ◽  
Basic Knowledge ◽  
Northern Coast

Fish assemblages are an important element of sandy beaches, as they are fundamental for these ecosystems' balance of energy. Descriptions of the structure of fish assemblages in the sandy beaches of northeastern Brazil are scarce; this is especially true for the state of Rio Grande do Norte, which northern coast is poorly studied. This study aimed to identify the fish fauna of São Cristóvão Beach and to determine their assemblage structure. Three trawlings, considered as replicates, were undertaken monthly, in the same day, during 10 minutes each time, parallel to the coastal line, and in the direction of current, from February 2010 to January 2011. To describe the general pattern of the fish assemblage, the abundance, frequency and trophic categories of each species were estimated. On São Cristóvão Beach, 8894 individuals were captured, belonging to 58 species, 48 genera and 28 families. The most abundant and frequent species were Pomadasys corvinaeformis (Steindachner, 1868), Cathorops spixii (Agassiz, 1829), Stellifer rastrifer (Jordan, 1889), Pellona harroweri (Fowler, 1917), Stellifer stellifer (Bloch, 1790), Chirocentrodon bleekerianus (Poey, 1867), Larimus breviceps Cuvier, 1830, Menticirrhus americanus (Linnaeus, 1758)and Conodon nobilis (Linnaeus, 1758). The most abundant trophic category was first order carnivores. The ichthyofauna of São Cristóvão Beach is diversified and the most representative families match those observed in sandy beach ecosystems from other Brazilian regions. The results presented here reflect the basic knowledge necessary to conduct further research in the region.

scholarly journals Environmental heterogeneity explains species turnover but not nestedness in fish assemblages of a Neotropical basin

2017 ◽  
Vol 29 (0) ◽  
Author(s):  
Oscar Eduardo Peláez ◽  
Filipe Manoel Azevedo ◽  
Carla Simone Pavanelli
Keyword(s):  
Species Composition ◽  
Beta Diversity ◽  
Environmental Variables ◽  
Environmental Heterogeneity ◽  
Fish Assemblages ◽  
Environmental Gradients ◽  
Species Turnover ◽  
Paraná River ◽  
Fish Diversity ◽  
Parana River

Abstract Aim: Heterogenous environments can contribute to maintain biodiversity. Traditionally beta diversity studies have focused on determining the effect of environmental variables on the total dissimilarity of species composition. However, decomposing beta diversity in species replacement and nestedness could give new insights on mechanisms affecting spatial patterns of biodiversity. We aimed to answer two main questions about spatial patterns of fish diversity in a Neotropical basin: 1) whether some regions contribute differently to fish diversity, and 2) whether species turnover and nestedness are explained by environmental gradients. Methods Sampling sites in the main channel and tributaries of the Upper Paraná River were sampled between 2013 and 2015. We partitioned beta diversity and tested the relationship of turnover and nestedness with environmental variables. Results 74 species were captured. Some of these species were restricted to different sites, contributing to variation in species composition. Hill numbers showed a trend for higher diversity in the tributaries than in Paraná River sampling sites, and the partition of beta diversity revealed that species replacement drove dissimilarity in species composition. Only total beta diversity and turnover were related to environmental variables, mainly conductivity and turbidity. Conclusions Species diversity and composition of fish assemblages in the Upper Paraná River could be related to environmental gradients. Overall, our results suggest that Paraná River tributaries contribute to increase environmental heterogeneity, and hence to maintain a high diversity and variation in species composition. For that reason, we strongly recommend preserving highly heterogeneous habitats in the region.

Drivers of diversity gradients of a highly mobile marine assemblage in a mesoscale seascape

2020 ◽  
Vol 638 ◽  
pp. 149-164
Author(s):  
GM Svendsen ◽  
M Ocampo Reinaldo ◽  
MA Romero ◽  
G Williams ◽  
A Magurran ◽  
...  
Keyword(s):  
Environmental Gradients ◽  
Regression Tree ◽  
Demersal Fish ◽  
Open Ocean ◽  
Shared Resources ◽  
Thermal Front ◽  
Boosted Regression Tree ◽  
Diversity Gradients ◽  
Α Diversity ◽  
Bottom Depth

With the unprecedented rate of biodiversity change in the world today, understanding how diversity gradients are maintained at mesoscales is a key challenge. Drawing on information provided by 3 comprehensive fishery surveys (conducted in different years but in the same season and with the same sampling design), we used boosted regression tree (BRT) models in order to relate spatial patterns of α-diversity in a demersal fish assemblage to environmental variables in the San Matias Gulf (Patagonia, Argentina). We found that, over a 4 yr period, persistent diversity gradients of species richness and probability of an interspecific encounter (PIE) were shaped by 3 main environmental gradients: bottom depth, connectivity with the open ocean, and proximity to a thermal front. The 2 main patterns we observed were: a monotonic increase in PIE with proximity to fronts, which had a stronger effect at greater depths; and an increase in PIE when closer to the open ocean (a ‘bay effect’ pattern). The originality of this work resides on the identification of high-resolution gradients in local, demersal assemblages driven by static and dynamic environmental gradients in a mesoscale seascape. The maintenance of environmental gradients, specifically those associated with shared resources and connectivity with an open system, may be key to understanding community stability.

scholarly journals Environmental Variation and How its Spatial Structure Influences the Cross-Shelf Distribution of High-Latitude Coral Communities in South Africa

Diversity ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 57 ◽  
Author(s):  
Sean N. Porter ◽  
Michael H. Schleyer
Keyword(s):  
South Africa ◽  
Continental Shelf ◽  
High Latitude ◽  
Environmental Variables ◽  
Environmental Gradients ◽  
High Tide ◽  
Environmental Variation ◽  
Shelf Edge ◽  
Spatial Differences ◽  
Coral Communities

Coral communities display spatial patterns. These patterns can manifest along a coastline as well as across the continental shelf due to ecological interactions and environmental gradients. Several abiotic surrogates for environmental variables are hypothesised to structure high-latitude coral communities in South Africa along and across its narrow shelf and were investigated using a correlative approach that considered spatial autocorrelation. Surveys of sessile communities were conducted on 17 reefs and related to depth, distance to high tide, distance to the continental shelf edge and to submarine canyons. All four environmental variables were found to correlate significantly with community composition, even after the effects of space were removed. The environmental variables accounted for 13% of the variation in communities; 77% of this variation was spatially structured. Spatially structured environmental variation unrelated to the environmental variables accounted for 39% of the community variation. The Northern Reef Complex appears to be less affected by oceanic factors and may undergo less temperature variability than the Central and Southern Complexes; the first is mentioned because it had the lowest canyon effect and was furthest from the continental shelf, whilst the latter complexes had the highest canyon effects and were closest to the shelf edge. These characteristics may be responsible for the spatial differences in the coral communities.

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