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 Do climate and fishing influence size-based indicators of Celtic Sea fish community structure?

2005 ◽  
Vol 62 (3) ◽  
pp. 405-411 ◽  
Author(s):  
Julia L. Blanchard ◽  
Nicholas K. Dulvy ◽  
Simon Jennings ◽  
James R. Ellis ◽  
John K. Pinnegar ◽  
...  
Keyword(s):  
Community Structure ◽  
Size Structure ◽  
Anthropogenic Impacts ◽  
Fishing Effort ◽  
Limited Area ◽  
Fish Community Structure ◽  
Community Metrics ◽  
Celtic Sea ◽  
Using Data ◽  
Sea Fish

Abstract Ecosystem-based management requires the development of indicators that allow anthropogenic impacts to be detected against the background of natural variation. Size-based community metrics are potentially useful indicators because of their theoretical foundation and practical utility. Temporal and spatial patterns in size-based community metrics for Celtic Sea fish are described and calculated using data from the English groundfish survey of the area (1987–2003). The results reveal that the size structure of the community has changed over time, and that a decrease in the relative abundance of larger fish was accompanied by an increase in smaller fish (4–25 g). Temporal analyses of the effects of fishing and climate variation suggest that fishing generally has had a stronger effect on size structure than changes in temperature. Therefore, size-based metrics respond clearly to the effects of fishing even in variable environments, reflecting the ubiquity of size-based processes in defining community structure and responses to mortality. Spatial analyses were inconclusive, probably owing to the limited area for which fishing effort, temperature, and survey data were all available.

Modelling recovery of Celtic Sea demersal fish community size-structure

2013 ◽  
Vol 140 ◽  
pp. 91-95 ◽  
Author(s):  
Samuel Shephard ◽  
Tak Fung ◽  
Axel G. Rossberg ◽  
Keith D. Farnsworth ◽  
David G. Reid ◽  
...  
Keyword(s):  
Fish Community ◽  
Size Structure ◽  
Demersal Fish ◽  
Community Size ◽  
Celtic Sea

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 Fishing and environment drive spatial heterogeneity in Celtic Sea fish community size structure

2011 ◽  
Vol 68 (10) ◽  
pp. 2106-2113 ◽  
Author(s):  
Samuel Shephard ◽  
Hans D. Gerritsen ◽  
Michel J. Kaiser ◽  
Holly S. Truszkowska ◽  
David G. Reid
Keyword(s):  
Spatial Heterogeneity ◽  
Fish Community ◽  
Size Structure ◽  
Fishing Effort ◽  
Trawl Survey ◽  
Weak Effect ◽  
Community Size ◽  
Negative Effect ◽  
Celtic Sea ◽  
Sea Fish

Abstract Shephard, S., Gerritsen, H. D., Kaiser, M. J., Truszkowska, H. S., and Reid, D. G. 2011. Fishing and environment drive spatial heterogeneity in Celtic Sea fish community size structure. – ICES Journal of Marine Science, 68: 2106–2113. The Large Fish Indicator (LFI) is a univariate size-based indicator of fish community state that has been selected to support the OSPAR fish community Ecological Quality Objective (EcoQO). To operate this EcoQO, a survey-based LFI for each OSPAR region needs to be developed. However, fish communities in these regions are spatially heterogeneous, and there is evidence of within-region spatial variation in the LFI that could confound an overall indicator series. For Celtic Sea trawl-survey sites, spline correlograms indicate positive spatial autocorrelation at a similar range (∼40 km) for the LFI and for fishing effort (h year−1) from vessel monitoring systems. Statistical models reveal a strong negative effect on annual LFI by site of fishing effort within a radius of 40 km. There was a weak effect of fishing within 20 km and no effect at 10 km. LFI also varied significantly with substratum and with local fish community composition identified by a resemblance matrix derived from the survey data. Finally, there was a weak effect of survey year on LFI. Spatial stratification of LFI calculations may be necessary when developing size-based indicators for OSPAR or Marine Strategy Framework Directive regions.

scholarly journals Quantifying heterogeneous responses of fish community size structure using novel combined statistical techniques

2016 ◽  
Vol 22 (5) ◽  
pp. 1755-1768 ◽  
Author(s):  
Abigail M. Marshall ◽  
Grant R. Bigg ◽  
Sonja M. van Leeuwen ◽  
John K. Pinnegar ◽  
Hua-Liang Wei ◽  
...  
Keyword(s):  
Fish Community ◽  
Size Structure ◽  
Statistical Techniques ◽  
Community Size

scholarly journals Redundancy in metrics describing the composition, structure, and functioning of the North Sea demersal fish community

2012 ◽  
Vol 69 (1) ◽  
pp. 8-22 ◽  
Author(s):  
Simon P. R. Greenstreet ◽  
Helen M. Fraser ◽  
Stuart I. Rogers ◽  
Verena M. Trenkel ◽  
Stephen D. Simpson ◽  
...  
Keyword(s):  
North Sea ◽  
Fish Community ◽  
Size Structure ◽  
Demersal Fish ◽  
Community Size ◽  
The North ◽  
Management Objectives ◽  
The North Sea ◽  
Composition Structure ◽  
And Function

Abstract Greenstreet, S. P. R., Fraser, H. M., Rogers, S. I., Trenkel, V. M., Simpson, S. D., and Pinnegar, J. K. 2012. Redundancy in metrics describing the composition, structure, and functioning of the North Sea demersal fish community. – ICES Journal of Marine Science, 69: 8–22. Broader ecosystem management objectives for North Sea demersal fish currently focus on restoring community size structure. However, most policy drivers explicitly concentrate on restoring and conserving biodiversity, and it has not yet been established that simply restoring demersal fish size composition will be sufficient to reverse declines in biodiversity and ensure a generally healthy community. If different aspects of community composition, structure, and function vary independently, then to monitor all aspects of community general health will require application of a suite of metrics. This assumes low redundancy among the metrics used in any such suite and implies that addressing biodiversity issues specifically will require explicit management objectives for particular biodiversity metrics. This issue of metric redundancy is addressed, and 15 metrics covering five main attributes of community composition, structure, and function are applied to groundfish survey data. Factor analysis suggested a new interpretation of the metric information and indicated that a minimum suite of seven metrics was necessary to ensure that all changes in the general health of the North Sea demersal fish community were monitored properly. Covariance among size-based and species-diversity metrics was low, implying that restoration of community size structure would not necessarily reverse declines in species diversity.

scholarly journals Ecology of sandflies (Diptera: Psychodidae) in a restricted focus of cutaneous leishmaniasis en Northern Venezuela: I. Description of the study area, catching methods and species composition

1987 ◽  
Vol 82 (1) ◽  
pp. 119-124 ◽  
Author(s):  
M. Dora Feliciangeli
Keyword(s):  
Species Composition ◽  
Cutaneous Leishmaniasis ◽  
Relative Abundance ◽  
Rare Species ◽  
Common Species ◽  
Term Study ◽  
Phlebotomine Sandfly ◽  
Phlebotomine Sandflies ◽  
The Common ◽  
Catching Methods

A study on the ecology of phlebotomine sandfly fauna in a restricted focus of cutaneous leishmaniasis in northern Venezuela was undertaken in order to investigate the species responsible for the transmission. The study area and catching methods for phlebotomine sandflies are described. A total of 9,061 females and 1,662 males were collected during a year-term study. 12 species of Lutzomya and 1 species of Brumptomya sp. were identified. Absolute and relative abundance and ocurrence for each species were determined. The rel ative occurrence allowed to distinguish the common species, viz. L. panamensis, L. ovallesi, L. gomezi, L. tinidadensis, L. atroclavata, L. cayennensis, L. shannoni and L. olmeca bicolor from the rare species vis., L. punctigeniculata, L. rangeliana, L. evansi and L. dubitans. General comments on the species composition of the sandfly fauna in this locality are made.

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