scholarly journals Monitoring zeebodemafval in de Noordzee en Waddenzee naar aanleiding van de containerramp met de MSC Zoe : Beam trawl survey en Demersal Fish survey 2019

2019 ◽  
Author(s):  
Joey Volwater ◽  
◽  
Ralf van Hal
Keyword(s):  
Demersal Fish ◽  
Trawl Survey ◽  
Beam Trawl ◽  
Beam Trawl Survey

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.

Recurrent Group Analysis of Species Assemblages of Demersal Fish in the Gulf of Guinea

1968 ◽  
Vol 25 (7) ◽  
pp. 1405-1421 ◽  
Author(s):  
E. W. Fager ◽  
A. R. Longhurst
Keyword(s):  
Survey Data ◽  
Computer Analysis ◽  
Group Analysis ◽  
Demersal Fish ◽  
Species Assemblages ◽  
Trawl Survey ◽  
Wide Sense ◽  
Subjective Analysis ◽  
Major Species ◽  
Species Groups

Recurrent species groups were formed by computer analysis from the data on occurrence of demersal fish at 480 trawl stations in the tropical eastern Atlantic; these recurrent groups were then marshalled into a small number of major species assemblages, or communities in the wide sense, on the basis of intergroup relationships. These assemblages proved to be remarkably similar in composition and ecology to the communities of demersal fish recognized earlier by a number of authors from their subjective analysis of trawling survey data in this region. The computer analysis provided finer detail on both the structure and distribution of the assemblages and their constituent groups. This confirmation of the reality of the subjectively recognized communities suggests (1) that the recognition of such assemblages by subjective methods has a place in the assessment of multispecies fish resources but (2) that where the method is practicable, the machine processing of recurrent species groups in the analysis of trawl survey data can be a valuable tool in resource evaluation.

scholarly journals Species composition and distribution of fishes and prawns in the Amur River channel

2020 ◽  
Vol 200 (2) ◽  
pp. 292-307
Author(s):  
V. N. Koshelev ◽  
N. V. Kolpakov
Keyword(s):  
Fish Species ◽  
Total Biomass ◽  
Trawl Survey ◽  
Amur River ◽  
Commercial Fish ◽  
The Amur River ◽  
Bottom Fish ◽  
Main Portion ◽  
Beam Trawl Survey ◽  
Species Composition And Distribution

istribution of fishes and prawns in the Amur River (40–960 km from the mouth) is described on results of the beam-trawl survey conducted in September-October, 2003 (57 trawl stations at the depth of 1.5–23.0 m). In total, 2584 ind. of 22 fish species and 1077 ind. of 1 invertebrate species (prawn Palaemon modestus) were caught. The highest species richness was registered for orders Cypriniformes (13 species) and Siluriformes (4 species). The fish and prawn stocks were evaluated as 32.161 . 106 ind. (583.8 t) for bottom and near-bottom fish and 4.887 . 106 ind. (8.8 t) for prawns. Two commercial fish species were the most abundant: catfishes Tachysurus brashnikowi (16.26 . 106 ind. or 32.9 % of total biomass) and T. sinensis (4.32 . 106 ind. or 24.0 % of total biomass); other 6 fish species with considerable biomass were lizard gudgeon Saurogobio dabryi (12.6 %), ussuri catfish T. ussuriensis (9.7 %), amur white-pinned gudgeon Romanogobio tenuicorpus (7.8 %), amur sturgeon Acipenser schrenckii (5.6 %), amur gudgeon Gobio cynocephalus (2.4 %), and kaluga Huso dauricus (0.6 %). Distribution density varied in the range of 0.01–2.57 g/m2 (on average 0.45 ± 0.27 g/m2) for fish and 0.005–0.044 g/m2 (0.021 ± 0.012 g/m2) for prawns. Abundance of both fish and prawns increased multifold towards the Amur mouth that correlated with increasing of forage benthos biomass in the same direction. So, the main portion of fish biomass (82.4 %) was distributed in the Amur River downstream (40–400 km from the mouth) and the prawn stock was concentrated completely in its lowermost part (50–150 km from the mouth).

scholarly journals Identifying Persistent Hot Spot Areas of Undersized Fish and Crustaceans in Southern European Waters: Implication for Fishery Management Under the Discard Ban Regulation

2021 ◽  
Vol 8 ◽  
Author(s):  
Giacomo Milisenda ◽  
Germana Garofalo ◽  
Fabio Fiorentino ◽  
Francesco Colloca ◽  
Francesc Maynou ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Fishery Management ◽  
Hot Spot ◽  
Demersal Fish ◽  
Fishing Effort ◽  
Trawl Survey ◽  
Management Actions ◽  
Management Measures ◽  
Fishery Policy ◽  
By Catch

The recent establishment of the “landing obligation” under the reformed EU Common Fishery Policy has the twofold objective of reducing the excessive practice of discarding unwanted catch at sea and encouraging more selective and sustainable fisheries. Within this context, the awareness of the spatial distribution of potential unwanted catches is important for devising management measures aimed to decrease discards. This study analyzed the distribution of Hot Spot density areas of demersal fish and crustaceans below the Minimum Conservation Reference Size (MCRS) in four different southern European seas: continental Portuguese coast, Catalan Sea, South of Sicily, Liguria and northern Tyrrhenian Seas using both bottom trawl survey data and information on the spatial distribution of commercial fisheries. Critical areas for discarding were identified as zones where the highest densities of individuals below MCRS were consistently recorded throughout a series of years. Results clearly showed a patchy distribution of undersized individuals in each investigated area, highlighting the overlap between high density patches of both discards and fishing effort. The present findings provide a relevant knowledge for supporting the application of spatial-based management actions, such as the designation of Fisheries Restricted Areas (FRAs), in order to minimize the by-catch of undersized specimens and improve the sustainability of demersal fisheries.

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.

scholarly journals Trends in cpue and related changes in spatial distribution of demersal fish species in the Kattegat and Skagerrak, eastern North Sea, between 1981 and 2003

2005 ◽  
Vol 62 (4) ◽  
pp. 671-682 ◽  
Author(s):  
Michele Casini ◽  
Massimiliano Cardinale ◽  
Joakim Hjelm ◽  
Francesca Vitale
Keyword(s):  
Spatial Distribution ◽  
Fish Species ◽  
General Pattern ◽  
Demersal Fish ◽  
Average Weight ◽  
Trawl Survey ◽  
Catch Per Unit Effort ◽  
Distribution Maps ◽  
Increasing Trend ◽  
Commercial Species

Abstract We explored the trends in ln-transformed catch per unit effort, defined as average weight (kg) per 1 h trawling, and the spatial distribution of 32 demersal fish species in the Kattegat and Skagerrak using International Bottom Trawl Survey data collected between 1981 and 2003. As in other areas, the biomass of roundfish species such as cod, pollack, hake, and ling drastically decreased during this period most likely owing to fishing pressure. However, other commercially important fish species, e.g. haddock, whiting, and some flatfish, showed a constant or increasing trend during the same period. Non-commercial species showed no or an increasing trend in ln-cpue, by as much as 40 times in hagfish. Furthermore, analyses of the spatial distribution of 14 selected fish species by means of distribution maps of ln-cpue suggested that fish stocks contracted and expanded in response to decrease and increase of the stock biomass, respectively, with some flatfish species (i.e. plaice and flounder) and hagfish representing the exceptions to this general pattern.

Changes in species composition of the demersal fish community in nearshore waters of Kodiak Island, Alaska

2000 ◽  
Vol 57 (6) ◽  
pp. 1169-1180 ◽  
Author(s):  
Franz J Mueter ◽  
Brenda L Norcross
Keyword(s):  
Species Composition ◽  
Major Part ◽  
Fish Community ◽  
Demersal Fish ◽  
Trawl Survey ◽  
Data Set ◽  
Forage Fishes ◽  
Kodiak Island ◽  
Trends Over Time ◽  
Over Time

We examined the species composition of the demersal fish and shrimp community in seven different areas in the nearshore waters of Kodiak Island based on trawl survey data. A major part of the variability in the data set was attributed to trends over time, indicating a significant change in species composition in the early 1980s. Results agree with work by others and show a shift from a community dominated by shrimp and small forage fishes to one dominated by large piscivorous gadid and flatfish species. The shift occurred rather abruptly in most areas between 1980 and 1982, but the pattern of change differed significantly among areas. Correlations between trends in the two groups of species were weak but were consistent with the hypothesis that the decline in shrimp and forage fishes followed, rather than preceded, the increase in large piscivorous fishes. The results suggest predation as a possible mechanism to explain the observed changes.

scholarly journals Estimating gear efficiency in a combined acoustic and trawl survey, with reference to the spatial distribution of demersal fish

2009 ◽  
Vol 67 (4) ◽  
pp. 668-676 ◽  
Author(s):  
Mathieu Doray ◽  
Stéphanie Mahévas ◽  
Verena M. Trenkel
Keyword(s):  
Spatial Distribution ◽  
Demersal Fish ◽  
Target Strength ◽  
Fish Length ◽  
Trawl Survey ◽  
Acoustic Backscattering ◽  
Scattering Coefficients ◽  
Fishing Vessels ◽  
Gear Efficiency ◽  
The Mean

Abstract Doray, M., Mahévas, S., and Trenkel, V. M. 2010. Estimating gear efficiency in a combined acoustic and trawl survey, with reference to the spatial distribution of demersal fish. – ICES Journal of Marine Science, 67: 668–676. Few analyses have been performed to estimate the efficiency of trawls targeting demersal fish using the ratio of catches and acoustic densities. In summer 2006, acoustic and fishing data were collected simultaneously over 3 d by three fishing vessels equipped with identical pelagic trawls in the Bay of Biscay. Variography identified moderate spatial autocorrelation in the acoustic backscatter at a mean scale of 3 km, a scale slightly smaller than the mean haul length (3.5 km), indicating that fish horizontal availability did not influence trawl efficiency. Acoustic backscattering densities expressed as nautical area scattering coefficients (NASCs) recorded in the trawled layer were compared with equivalent NASC (ENASC) values calculated from the species composition in the trawl, fish-length structure, and available relationships between target strength and fish length. Estimates of trawl efficiency for hake-dominated trawls were computed as the slopes of the relationships ENASC = 0.008 NASC and ENASC = 0.18 NASC0.31 for trawls made by day and night, respectively. For the whole demersal community, the relationships were ENASC = 0.022 NASC and ENASC = 0.17 NASC0.33 for trawls made by day and night, respectively.

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