Comparison of catches taken in dual-mesh beach seines of two different lengths

1998 ◽  
Vol 49 (6) ◽  
pp. 513
Author(s):  
M. A. Vanderklift ◽  
C. A. Jacoby ◽  
P. Horwitz
Keyword(s):  
Species Composition ◽  
Size Structure ◽  
Small Fish ◽  
Large Fish ◽  
Spatial And Temporal Patterns ◽  
Assemblage Composition ◽  
Different Types ◽  
Commercially Important ◽  
Dual Mesh ◽  
Important Fish

This study examined the species composition and size structure of fish and macro-invertebrates captured by two dual-mesh beach seines of different lengths. Both nets captured small fish, large fish and juveniles. The longer net appeared to be the best choice as a sampling tool, but support for this choice was not strong. The assemblages caught by the two nets differed, but these differences did not mask overall spatial and temporal patterns in assemblage composition. The longer seine caught more species, but estimates of total densities for all individuals and densities of three common, commercially important fish species did not differ consistently between the two nets. Comparisons and generalizations based on studies that use different types of seines should be interpreted cautiously because design features may influence results in inconsistent and unpredictable ways.

scholarly journals Historical discarding in Mediterranean fisheries: a fishers' perception

2015 ◽  
Vol 72 (9) ◽  
pp. 2600-2608 ◽  
Author(s):  
Dimitrios Damalas ◽  
Christos D. Maravelias ◽  
Giacomo C. Osio ◽  
Francesc Maynou ◽  
Mario Sbrana ◽  
...  
Keyword(s):  
Species Composition ◽  
Market Demand ◽  
Sampling Protocol ◽  
The Past ◽  
Regulatory Constraints ◽  
Fishing Strategies ◽  
Commercially Important ◽  
Trawl Fisheries ◽  
Important Fish

Abstract Discarding of commercially important fish species in the bottom trawl fisheries in the northern Mediterranean Sea was investigated by soliciting the long-term recollections of fishers engaged or formerly engaged in such fisheries. The main aim of our investigation was to describe the prevalence of discarding and its evolution over the past 70 years using information gathered through individual questionnaire-based interviews with fishers from ports in Spain, Italy, and Greece, following a standardized sampling protocol. Although it proved impossible to derive absolute estimates of the volume of discarded catches over the period investigated, we conclude that over the past 70 years, discarding as a practice has gradually increased in the northern Mediterranean trawl fisheries and has been accompanied by a shift in the species composition of the discarded catch. While discarding can occur for a number of reasons, our investigations indicate that discarding in the past was mostly driven by market demand, but recent legal and regulatory constraints have led to changes in fishing strategies and became a significant reason for discards.

scholarly journals Size-selective fishing drives species composition in the Celtic Sea

2012 ◽  
Vol 69 (2) ◽  
pp. 223-234 ◽  
Author(s):  
Samuel Shephard ◽  
Tak Fung ◽  
Jennifer E. Houle ◽  
Keith D. Farnsworth ◽  
David G. Reid ◽  
...  
Keyword(s):  
Species Composition ◽  
Relative Abundance ◽  
Size Structure ◽  
Large Species ◽  
Strongly Correlated ◽  
Large Fish ◽  
Fish Community Structure ◽  
Community Size ◽  
Two Indices ◽  
Celtic Sea

Abstract Shephard, S., Fung, T., Houle, J. E., Farnsworth, K. D., Reid, D. G., and Rossberg, A. G. 2012. Size-selective fishing drives species composition in the Celtic Sea. – ICES Journal of Marine Science, 69: 223–234. Fishing alters community size structure by selectively removing larger individual fish and by changing the relative abundance of different-sized species. To assess the relative importance of individual- and species-level effects, two indices of fish community structure were compared, the relative abundance of large fish individuals (large fish indicator, LFI) and the relative abundance of large fish species (large species indicator, LSI). The two indices were strongly correlated for empirical data from the Celtic Sea and for data from simulated model communities, suggesting that much of the variability in the LFI is caused by shifts in the relative abundance of species (LSI). This correlation is explained by the observation that most of the biomass of a given species is spread over few length classes, a range spanning the factor 2 of individual length, such that most species contributed predominantly to either the small or the large component of the LFI. The results suggest that the effects of size-selective fishing in the Celtic Sea are mediated mainly through changes in community composition.

scholarly journals Composition and Occurrence of Fish Fauna from Thanbyuzayat Township, Mon Coastal Area

Bionatura ◽  
2020 ◽  
Vol 5 (4) ◽  
pp. 1363-1370
Author(s):  
Zarni Ko Ko
Keyword(s):  
Species Composition ◽  
Fish Species ◽  
Dominant Species ◽  
Fish Fauna ◽  
Important Species ◽  
Foreign Countries ◽  
Commercially Important ◽  
Bombay Duck ◽  
Study Sites ◽  
Important Fish

A total of 48 species of fish fauna were identified during the present study period. The dominant species of fish were found under order Perciformes in all study areas. The most species composition (40) was recorded in Setse fish landing area. The commercially important fish species were mostly found in Kyaikkhami area. Moreover, 17 species of fish were exported to other regions and foreign countries. Among the fish species, species such as Threadfin (Polynemidae), Croaker (Sciaenidae), Hilsa (Clupeidae), Bombay duck (Harpadontidae), Anchovy (Engraulidae), and Pomfret fish (Stomateidae) were the most economically important species. Bombay duck and Anchovy (especially Coilia dussumieri) were more abundant (70%) at the present study sites. Harpodon nehereus and Coilia species were the leading food employed as fresh and dried for local people in the present study areas. Key words: Ichthyology, Taxonomy, Compositions, Occurrence, fish landing centers, Thanbyuzayat Township, Mon Coastal Areas.

Size Changes, Mortality, and Equilibrium Yields in an Exploited Stock of American Plaice (Hippoglossoides platessoides)

1969 ◽  
Vol 26 (5) ◽  
pp. 1205-1235 ◽  
Author(s):  
P. M. Powles
Keyword(s):  
Mesh Size ◽  
Food Competition ◽  
Mortality Factor ◽  
Otter Trawl ◽  
Small Fish ◽  
Large Fish ◽  
Age Composition ◽  
Instantaneous Rate ◽  
Factors Affecting ◽  
Ecological Dominance

Records from research surveys and commercial landings for American plaice from the Magdalen Shallows, or the southwestern Gulf of St. Lawrence, showed decreases in percentage of old, large fish and in catch per unit of effort from 1955 to 1962. The changes in age composition were clearly relatable to the fishery, which was mainly by otter trawl. Ricker models indicated that wastage of deck-exposed subcommercial plaice is currently a greater mortality factor than predation by cod. Increased landings in particular years were associated with successful year-classes. Other factors affecting landings were annual differences in fleet dispersal, which were related to movements of cod, a cohabiting species. No clear decrease or increase in absolute recruitment of plaice was demonstratable because quantitative comparisons of research surveys by different vessels using different gears and with different skippers, would be misleading.Mortality estimates of adult plaice by three methods showed agreement, indicating that instantaneous rate of natural mortality was between 0.09 and 0.13. The instantaneous rate of fishing for 1957–62 was 0.46. Increasing mesh-size would reduce cod catches and have little effect in conserving plaice, but marketing small fish would increase plaice landings. Voluntary release of small plaice promptly on capture would help maintain the stock, as would reduction in numbers of large cod, the main predator of small plaice. Increased numbers of small cod since 1959, as reported by other workers, could result in greater food competition with small plaice, effectively reinforcing the ecological dominance of cod over plaice.

Predation by Sharks on the Grey Seal (Halichoerus grypus) in Eastern Canada

1983 ◽  
Vol 40 (3) ◽  
pp. 267-271 ◽  
Author(s):  
Paul Brodie ◽  
Brian Beck
Keyword(s):  
Key Words ◽  
Population Size ◽  
Halichoerus Grypus ◽  
Longline Fishery ◽  
Grey Seal ◽  
Eastern Canada ◽  
The Past ◽  
Harbour Seals ◽  
Commercially Important ◽  
Important Fish

The increase in population size of the grey seal (Halichoerus grypus) off eastern Canada over the past 20 yr may be attributed to a decrease in shark stocks, their supposed predators. Reduction of the shark population is presumed to have resulted from a directed longline fishery and, of greater significance, from a change in the fishery for swordfish (Xiphias gladius) from selective harpooning to pelagic longlining, which has produced a large bycatch of sharks. The resulting enhanced survival of grey seals is reflected in greater infestation of commercially important fish species by the codworm (Phocanema decipiens).Key words: grey seals, harbour seals, sharks, swordfish, codworm, predation, fisheries

scholarly journals Ecology of Cladocera species from Central America based on subfossil assemblages

2016 ◽  
Vol 1 (1S) ◽  
Author(s):  
Marta Wojewódka ◽  
Edyta Zawisza ◽  
Sergio Cohuo ◽  
Laura Macario-González ◽  
Antje Schwalb ◽  
...  
Keyword(s):  
Species Composition ◽  
Central America ◽  
Wide Spectrum ◽  
Great Majority ◽  
Common Species ◽  
Quantitative Composition ◽  
Habitat Conditions ◽  
Mountain Regions ◽  
Different Types ◽  
Lowland Lakes

<p>Cladocera species composition was analyzed in surface sediments of 29 lakes in Central America (Guatemala, El Salvador and Honduras). The material studied was collected with an Ekman grab in autumn 2013 from lakes located in lowland, highland and mountain regions. The study revealed high variability in qualitative and quantitative composition of subfossil Cladocera. A total of 31 Cladocera species (5 planktonic and 26 littoral) were identified, as well as 4 morphotypes that could not be identified (NRR<em> </em>1-4). Planktonic Bosminidae<em> </em>and<em> </em>Daphniidae were the most abundant families. Daphniidae were restricted to water bodies in mountain regions, whereas Bosminidae were widely distributed in lakes with different abiotic conditions. Moreover, Bosminidae species also occurred in highly mineralized waters (&gt; 900 µS cm<sup>-1</sup>). The great majority of the identified Cladocera species belonged to the littoral family Chydoridae. <em>Chydorus </em>cf.<em> sphaericus</em> was the most common species (found in 20 lakes), which probably reflects its tolerance to a wide spectrum of habitat conditions. Cluster analysis discriminated 6 groups of Cladocera species with a high correlation level within groups (≥0.8), which showed different types of correlation with lake characteristics and environmental variables. Canonical correspondence analysis (CCA) showed that altitude and secondly water electrical conductivity were the most important drivers of Cladocera species composition in the region studied. Furthermore, CCA analysis indicated lowland lakes with low water transparency were also characterized by peculiar species assemblages. <strong></strong></p>

scholarly journals A highly contiguous nuclear genome assembly of the mandarinfish Synchiropus splendidus (Syngnathiformes: Callionymidae)

2021 ◽  
Author(s):  
Martin Stervander ◽  
William A Cresko
Keyword(s):  
Genome Assembly ◽  
Nuclear Genome ◽  
Phylogenetic Position ◽  
Blue Color ◽  
Long Reads ◽  
The Family ◽  
Commercially Important ◽  
Genomic Resource ◽  
Genome Assemblies ◽  
Important Fish

Abstract The fish order Syngnathiformes has been referred to as a collection of misfit fishes, comprising commercially important fish such as red mullets as well as the highly diverse seahorses, pipefishes, and seadragons—the well-known family Syngnathidae, with their unique adaptations including male pregnancy. Another ornate member of this order is the species mandarinfish. No less than two types of chromatophores have been discovered in the spectacularly colored mandarinfish: the cyanophore (producing blue color) and the dichromatic cyano-erythrophore (producing blue and red). The phylogenetic position of mandarinfish in Syngnathiformes, and their promise of additional genetic discoveries beyond the chromatophores, made mandarinfish an appealing target for whole genome sequencing. We used linked sequences to create synthetic long reads, producing a highly contiguous genome assembly for the mandarinfish. The genome assembly comprises 483 Mbp (longest scaffold 29 Mbp), has an N50 of 12 Mbp, and an L50 of 14 scaffolds. The assembly completeness is also high, with 92.6% complete, 4.4% fragmented, and 2.9% missing out of 4,584 BUSCO genes found in ray-finned fishes. Outside the family Syngnathidae, the mandarinfish represents one of the most contiguous syngnathiform genome assemblies to date. The mandarinfish genomic resource will likely serve as a high-quality outgroup to syngnathid fish, and furthermore for research on the genomic underpinnings of the evolution of novel pigmentation.

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