Vertical Migration by Demersal Fish in the Northwest Atlantic

1966 ◽  
Vol 23 (1) ◽  
pp. 109-139 ◽  
Author(s):  
F. W. H. Beamish
Keyword(s):  
Seasonal Changes ◽  
General Pattern ◽  
Size Composition ◽  
Demersal Fish ◽  
Large Fish ◽  
Diurnal Difference ◽  
Commercially Important ◽  
Nova Scotian ◽  
Demersal Species ◽  
Trawl Catches

Observations on vertical patterns of migration were made on the Nova Scotian and Gulf of St. Lawrence fishing banks. The commercially important demersal species, cod, haddock, and redfish, were usually closely associated with bottom by day and moved off after dark. While this is the general pattern, variations occurred. Thus, on cloudy or dull days, redfish may remain in mid water. Cod did not always return to the seabed by day. Haddock, usually more closely associated with bottom than the other species, sometimes moved considerable distances from the seabed. Generally, concentrations of fish on bottom by day dispersed in mid water.In accord with vertical patterns of migration, bottom trawl catches were generally the lower by night. There was some suggestion of seasonal changes in the relation between day and night catches of cod and haddock. A suggestion of diurnal variation in size composition was found for haddock and yellowtail. More small haddock were taken by day than by night. Catches of large haddock tended to be the larger at night. Small yellowtail were the more abundant in night tows. No significant diurnal difference was found for large fish.

scholarly journals Microplastic pollution of commercial fishes from coastal and offshore waters, Japan

2021 ◽  
Author(s):  
Mitsuharu Yagi ◽  
Tsunefumi Kobayashi ◽  
Yutaka Maruyama ◽  
Sota Hoshina ◽  
Satoshi Masumi ◽  
...  
Keyword(s):  
East China Sea ◽  
Marine Environment ◽  
Deep Sea ◽  
Demersal Fish ◽  
Pelagic Fish ◽  
Polymer Composition ◽  
Species Variation ◽  
Habitat Depth ◽  
Commercially Important ◽  
Demersal Species

Microplastics (MPs) pollution is a worldwide issue in the marine environment. There is growing concern of consuming MPs through fish, yet the current contamination status of fish collected from the deep sea surrounding Japan remains limited. We present baseline data on MPs in commercially important fishes from the coastal and offshore waters near Kyushu, Japan (East China Sea). We examined the MPs in the digestive tracts of two pelagic (n = 150 in total) and five demersal species (n = 235 in total). The fish were caught by pole and line, and bottom trawl at different geographical positions. The MPs in pelagic fish (39.1 %) were higher than demersal fish (10.3 %) and of larger sizes. The MPs correlated with habitat depth and type. There was species variation in the shape and polymer composition of MPs. These results increase our understanding of the heterogeneous uptake of MPs by fishes.

Long-term changes in the diversity, abundance and size composition of deep sea demersal teleosts from the Azores assessed through surveys and commercial landings

2019 ◽  
Vol 32 ◽  
pp. 25 ◽  
Author(s):  
Régis V.S. Santos ◽  
Wendell M.M.L. Silva ◽  
Ana M. Novoa-Pabon ◽  
Hélder M. Silva ◽  
Mario R. Pinho
Keyword(s):  
Deep Sea ◽  
Linear Models ◽  
Fork Length ◽  
Size Composition ◽  
Demersal Fish ◽  
Scientific Data ◽  
Marine Habitat ◽  
Important Species ◽  
Commercially Important

To obtain important baseline information about population dynamics and to provide valuable insights about the possible effects of artisanal fishing on the demersal fish community, this study had three specific objectives: (1) to update the annotated list of demersal teleost species occurring in the Azores (mid-North Atlantic); (2) to describe their depth distribution and related fishery information; and (3) to evaluate annual changes in their observed abundance and length composition. To do this, a time series with about 25 years of scientific data from the commercial fishery and surveys was analyzed. The demersal teleost community was represented by 213 species, predominantly deep-water species, reflecting the main marine habitat in the Azores region. Fishery takes place mainly in the intermediate strata (200–600 m), where the most commercially important species occur. No changing in the fork length (LF) distribution toward small individuals caused by size-selective fishing was detected in this study. The high variability observed in the LF data indicates the need for more accurate studies considering alternative statistical analyses (e.g., generalised linear models) to examine the possible factors (e.g. depth coverage, gear configuration, soak time, and fishing area) that cause this variability. On the other hand, the abundance indices of some commercially important species appear to have declined (Phycis phycis, Pontinus kuhlii, Conger conger, Beryx splendens and B. decadactylus), while others appear to be more stable (Helicolenus dactylopterus) or even increasing (Mora moro). Although the available data are insufficient for a formal assessment on the status of exploited populations, the long-term analysis of commercial landings and survey data was used as a basis to assess deep sea demersal teleost fisheries of the Azores, under a precautionary approach.

scholarly journals The demersal fish composition and catch per unit effort of mini bottom trawl at the coast of Demak Regency Central Java

2021 ◽  
Vol 322 ◽  
pp. 03006
Author(s):  
Naliyana Fitriya ◽  
Nahlah Alfiatuunisa ◽  
Suwarman Partsuwiryo ◽  
Eko Setyobudi
Keyword(s):  
Demersal Fish ◽  
Bottom Trawl ◽  
North Coast ◽  
Catch Per Unit Effort ◽  
The North ◽  
Central Java ◽  
Unit Effort ◽  
Trichiurus Lepturus ◽  
Trawl Fishing ◽  
Trawl Catches

Demak is a coastal area on the North Coast of Java with a large enough potential for demersal fish resources. This research aimed to determine the composition, the length and weight distribution, and catch per unit effort (CPUE) of demersal fish caught using mini bottom trawl at the north coast of Demak Regency. The research was carried out in October-December 2020 by observation of ten trips of mini bottom trawl fishing. Each fish captured was then grouped by type, identified, and measured its length and weight. The result showed that 38 species consist of 31 fishes, four mollusks, and three crustaceans. The fish captured dominated by pony fish (Leiognathus equulus) as much as 31.23% and largehead hairtail (Trichiurus lepturus) of 23.52%. The catch per unit effort (CPUE) average of mini bottom trawl was 44.77 kg/trip. Mainly fish (more than 95%) caught in small size compared it’s the maximum attainable length (L-max), with all the weight ranges from 0.3 to 520 g and more than 98% sized 0.3-80 g. Mini bottom trawl catches many types of fish and small size; therefore, mini bottom trawl is classified as a type of fishing gear with a very low selectivity level.

Abundance of demersal fish resources in the Persian Gulf and Oman Sea

2006 ◽  
Vol 86 (6) ◽  
pp. 1455-1462 ◽  
Author(s):  
T. Valinassab ◽  
R. Daryanabard ◽  
R. Dehghani ◽  
G.J. Pierce
Keyword(s):  
Persian Gulf ◽  
Central Area ◽  
Demersal Fish ◽  
Total Biomass ◽  
Trawl Survey ◽  
Important Species ◽  
Fish Resources ◽  
Oman Sea ◽  
Commercially Important ◽  
The Persian Gulf

We report on results of a trawl survey during 2003–2004 to assess the abundance of demersal fish resources in the Persian Gulf and Oman Sea. Samples were taken at a total of 316 trawl stations selected following a stratified random procedure. Catch rates (catch per unit area, CPUA) and total biomass were estimated. Total demersal fish biomass was estimated to be approximately 73,000 tonnes in Persian Gulf waters and approximately 39,000 tonnes in the Oman Sea. The lowest CPUA was recorded in the west of the study area (stratum A, approximately 1700 kg/n.m.2) and the highest in the east (stratum Q, 13943.4 kg/n.m.2), although density of commercially important species was higher in the central area (stratum K). Catch rate and biomass varied significantly in relation to seabed depth. Commercially important demersal species made up around 60% of the estimated total biomass. The most abundant species groups were rays, catfish, grunts, nemipterids and carangids. Several important species (e.g. silver pomfret, croakers and sharks) appear to have declined since the late 1970s while others, such as rays and catfish, have increased.

scholarly journals Changes in species diversity and size composition in the Firth of Clyde demersal fish community (1927–2009)

2011 ◽  
Vol 279 (1728) ◽  
pp. 543-552 ◽  
Author(s):  
M. R. Heath ◽  
D. C. Speirs
Keyword(s):  
Species Diversity ◽  
Fish Community ◽  
Regional Scale ◽  
Size Composition ◽  
Demersal Fish ◽  
Maximum Length ◽  
Species Evenness ◽  
Large Maximum ◽  
Lobster Fishery ◽  
By Catch

Following the repeal in 1962 of a long-standing ban on trawling, yields of demersal fish from the Firth of Clyde, southwest Scotland, increased to a maximum in 1973 and then declined until the directed fishery effectively ceased in the early 2000s. Since then, the only landings of demersal fish from the Firth have been by-catch in the Norway lobster fishery. We analysed changes in biomass density, species diversity and length structure of the demersal fish community between 1927 and 2009 from scientific trawl surveys, and related these to the fishery harvesting rate. As yields collapsed, the community transformed from a state in which biomass was distributed across numerous species (high species evenness) and large maximum length taxa were common, to one in which 90 per cent of the biomass was vested in one species (whiting), and both large individuals and large maximum length species were rare. Species evenness recovered quickly once the directed fishery ceased, but 10 years later, the community was still deficient in large individuals. The changes partly reflected events at a larger regional scale but were more extreme. The lag in response with respect to fishing has implications for attempts at managing a restoration of the ecosystem.

Temporal changes in a demersal fish and cephalopod community of an unexploited coastal area in Northern Australia

1984 ◽  
Vol 35 (6) ◽  
pp. 747 ◽  
Author(s):  
SF Rainer
Keyword(s):  
Water Temperature ◽  
Seasonal Changes ◽  
Fish Community ◽  
Demersal Fish ◽  
Temporal Changes ◽  
Tropical Fish ◽  
Trawl Survey ◽  
Depth Range ◽  
Local Abundance ◽  
Different Seasons

A trawl survey of the south-eastern Gulf of Carpentaria carried out at the beginning of a commercial prawn fishery in the 1960s provided data on the demersal fish of an unexploited tropical fish community. The extent of temporal variation in this community was investigated using abundance data on 359 taxa of fish and cephalopods over 13 months in 1963-1964. Seasonal changes in water temperature and salinity were large, particularly in nearshore waters. Catch rates and species richness in nearshore waters were highest during summer, and in offshore waters during autumn or winter. Shannon diversity was variable, with no clear seasonal component. Temporal changes in community composition resulted in large changes between different seasons in the structure of site groups derived by classification; temporal effects within seasons were also found. The numerically dominant species were the leatherjackets Paramonacanthus spp., the ponyfish Equulites leuciscus, the tripodfish Tripodichthys blochii, and the saury Saurida undosquamis. Squid, the ponyfish Leiognathus sp. nr blochi, the butterfly-bream Nemipterus tolu and the grunter Pomadasys maculatus were seasonally abundant. Although species were restricted in their depth range, discrete communities that maintained their identity in different seasons were apparently absent. The relative abundance of many species varied substantially wirh season and probably also over a longer period. Small changes in local abundance were often associated with movement to deeper water at times of high nearshore water temperature (summer) or of reduced nearshore salinity (autumn). Large seasonal changes occurred in the local abundance of estuarine and semidiadromous species. The community shared many species with the demersal fish community of the Gulf of Thailand. It is suggested that similar structural changes in the fish community of the Gulf of Carpentaria may occur in response to intensive fishing. Further research on the effects of demersal fishing and on the interactions of the demersal fish community with commercially important crustaceans is necessary.

Biometrics Variation and Directional Preferences of Immature Robins (Erithacus rubecula) Caught in Northern Italy during Autumn Migration in 2005

Ring ◽  
2007 ◽  
Vol 29 (1-2) ◽  
pp. 107-120
Author(s):  
Katarzyna Rosińska ◽  
Karolina Adamska
Keyword(s):  
Seasonal Changes ◽  
Wing Length ◽  
General Pattern ◽  
Tail Length ◽  
Northern Italy ◽  
Wing Shape ◽  
Autumn Migration ◽  
Erithacus Rubecula ◽  
Increasing Trend ◽  
Migration Dynamics

Biometrics Variation and Directional Preferences of Immature Robins (Erithacus rubecula) Caught in Northern Italy during Autumn Migration in 2005 Inter-seasonal changes of biometry and preferred migration directions of Robins were studied according to data collected during autumn migration in northern Italy at the Arosio Bird Observatory (45°43'N, 9°12'E). Altogether 598 immature Robins were caught and 187 orientation tests were performed. Wing, tail and tarsus length, wing shape and weight were analysed in subsequent five migration waves distinguished according to migration dynamics. General pattern of migration as well as graphs with distribution of preferred directions in subsequent waves were prepared. In the case of tail length and weight their average values in subsequent waves were significantly different. Decrease of wing length was noted along the season. On the contrary, increasing trend was observed in the case of tail length and wing shape. Results of orientation tests showed that SSE direction was predominant (34%). SW direction was not clearly marked and its percentage was 23%. Distribution of directions slightly changed in subsequent migration waves. Noted results suggest passage of Robins heading to the Mediterranean basin and Apennine winter quarters. Obtained inter-seasonal changes of biometry and preferred directions can be an effect of differences in migration time between this groups or gradual inflow of more northern populations what the authors discuss here.

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