scholarly journals Seasonal and temporal trends in metrics of fish community for otter-trawl discards in a Mediterranean ecosystem

2008 ◽  
Vol 65 (4) ◽  
pp. 539-550 ◽  
Author(s):  
K. Tsagarakis ◽  
A. Machias ◽  
M. Giannoulaki ◽  
S. Somarakis ◽  
I. Karakassis
Keyword(s):  
Fish Community ◽  
Eastern Mediterranean ◽  
Temporal Trends ◽  
Demersal Fish ◽  
Trophic Levels ◽  
Otter Trawl ◽  
Mediterranean Ecosystem ◽  
Taxonomic Distinctness ◽  
Fishing Season ◽  
Trawl Fishery

Abstract Tsagarakis, K., Machias, A., Giannoulaki, M., Somarakis, S., and Karakassis, I. 2008. Seasonal and temporal trends in metrics of fish community for otter-trawl discards in a Mediterranean ecosystem. – ICES Journal of Marine Science, 65: 539–550. Trends in discard to marketed ratios, size spectra, diversities, and trophic levels of the demersal fish community were examined using data from a seasonally closed commercial trawl fishery in the eastern Mediterranean Sea (Ionian Sea), over a period of about 10 years. Trends were also examined for the artificial fractions derived from the discarding process (the marketed, the discarded, and the non-marketed clusters of the catch), as well as for the “big” and “small” fractions (defined by the size at which 50% of all specimens were discarded). The ratio of the discarded/marketed catch fluctuated greatly. Two commercial (Merluccius merluccius, and Mullus barbatus) and two non-marketed species (Lepidotrigla cavillone, and Argentina sphyraena) were the characteristic species of the fractions. A declining trend with time was observed for the examined time-series for species richness (S), Margalef’s d, and average taxonomic distinctness (Δ+), whereas the variation in taxonomic distinctness (Λ+) increased. The composition and/or trophic level of discards in relation to the marketed catch seemed to be indicative of the exploitation state of the demersal community: differences between the discarded and marketed fractions were high at the beginning of the fishing season (autumn), but the values of the indices converged at the end of the fishing season (spring). These changes could be attributed to alternative discarding strategies for certain species in response to increased cumulative fishing mortality towards the end of the period.

scholarly journals Species richness, taxonomic diversity, and taxonomic distinctness of the deep-water demersal fish community on the Northeast Atlantic continental slope (ICES Subdivision VIa)

2010 ◽  
Vol 68 (2) ◽  
pp. 365-376 ◽  
Author(s):  
Neil Campbell ◽  
Francis Neat ◽  
Finlay Burns ◽  
Phil Kunzlik
Keyword(s):  
Species Richness ◽  
Continental Slope ◽  
Deep Water ◽  
Fish Community ◽  
Temporal Trends ◽  
Taxonomic Diversity ◽  
Demersal Fish ◽  
Taxonomic Distinctness ◽  
Northeast Atlantic ◽  
Water Fish

Abstract Campbell, N., Neat, F., Burns, F., and Kunzlik, P. 2011. Species richness, taxonomic diversity, and taxonomic distinctness of the deep-water demersal fish community on the Northeast Atlantic continental slope (ICES Subdivision VIa). – ICES Journal of Marine Science, 68: 365–376. The fish community on the Atlantic deep continental shelf and upper slope to the northwest of Scotland has been the subject of biological studies for more than a century, and subject to bottom-trawl fishing for around 25 years. In this work, we examine trends in biodiversity of the deep-water demersal fish community revealed by a decade of trawl surveys by Marine Scotland—Science. The composition and structure of the fish assemblage was described using species richness as well as the descriptors of community interrelatedness: taxonomic diversity (Δ) and taxonomic distinctness (Δ*). Results revealed no temporal trends in community composition. The most significant factor in determining richness and taxonomic diversity of the demersal fish fauna was depth, and to a lesser extent latitude. Diversity and distinctness decreased with increasing depth and showed a complex relationship with latitude, while richness peaked at depths around 1400 m. This study shows taxonomic measures of diversity and distinctness to be sensitive indicators of ecological conditions in the deep-water fish community, with respect to depth and latitude, and the fact that no temporal trends were detected suggests that the structure of the fish community at exploitable depths on the Scottish slope has remained stable over the period 1998–2008. These findings imply that care should be taken when planning spatial measures designed to safeguard deep-water fish biodiversity because the optimal area recommended for protection is strongly dependent on the choice of metric used.

scholarly journals Demersal fish community on the inner shelf of Ubatuba, southeastern Brazil

1998 ◽  
Vol 46 (2) ◽  
pp. 93-109 ◽  
Author(s):  
Gecely R. A. Rocha ◽  
Carmen L. D. B. Rossi-Wongtschowski
Keyword(s):  
Continental Shelf ◽  
Coastal Water ◽  
Fish Community ◽  
Species Abundance ◽  
Fish Fauna ◽  
Sampling Period ◽  
Demersal Fish ◽  
Southeastern Brazil ◽  
Otter Trawl ◽  
South Atlantic Central Water

Fluctuations in the distribution and abundance of demersal fishes collected by otter trawl on the continental shelf of Ubatuba were examined over a two-year sampling period, in an area up to 50 m depth. A total of 111 species were collected. Seasonal and annual fluctuations in species abundance were related to differences in the distribution of Coastal Water and South Atlantic Central Water masses. The demersal fish fauna in the area was divided into three ecologically distinct communities: Tropical Sciaenid, Subtropical Sciaenid, and Gerreid-Haemulid. The most important one is the Tropical Sciaenid Community, characterized by Ctenosciaena gracilicirrhus, Paralonchurus brasiliensis, and Cynoscion jamaicensis.

Trophic ecology of the mid-slope demersal fish community off southern Tasmania, Australia

2002 ◽  
Vol 53 (1) ◽  
pp. 59 ◽  
Author(s):  
C. M. Bulman ◽  
X. He ◽  
J. A. Koslow
Keyword(s):  
Fish Community ◽  
Trophic Ecology ◽  
Diet Breadth ◽  
Demersal Fish ◽  
Benthic Invertebrate ◽  
Trophic Levels ◽  
Trophic Guilds ◽  
Orange Roughy ◽  
Eastern Australia ◽  
Australasian Region

The demersal fish community on the mid-slope off southern Tasmania in south-eastern Australia is dominated by orange roughy Hoplostethus atlanticus (Trachichthyidae), several species of oreosomatids, macrourids, squalids, alepocephalids and a synaphobranchid eel. Cluster analysis based on diet dissimilarities of proportional prey weight identified five major trophic guilds: pyrosome-feeders, crustacean feeders, piscivores, benthopelagic omnivores and benthic-invertebrate feeders. Overall, the fish fed predominantly on pelagic or benthopelagic prey, consistent with other trophic studies in the Australasian region and the Northern Hemisphere. H. atlanticus, warty dory Allocyttus verrucosus, and the macrourid Coryphaenoides serrulatus were benthopelagic omnivores that ate mesopelagic fishes, crustaceans and squid. The first two species ate more mesopelagic fishes as their sizes increased. The squalids were predominantly piscivorous but might also scavenge. Macrourids were benthic-invertebrate feeders, pelagic crustacean feeders or benthopelagic omnivores. The alepocephalids and the smooth oreo Pseudocyttus maculatus were pyrosome-feeders. No seasonal variation in diet was found for any species. Ecological indices varied within each guild. Benthopelagic omnivores and piscivores had the largest diet breadth, evenness and diversity. Trophic levels ranged from 3.0 for pyrosome-feeders to 4.9 for piscivores and the overall average for the community was 3.7.

Dissolved oxygen and temperature best predict deep-sea fish community structure in the Gulf of California with climate change implications

2020 ◽  
Vol 637 ◽  
pp. 159-180
Author(s):  
ND Gallo ◽  
M Beckwith ◽  
CL Wei ◽  
LA Levin ◽  
L Kuhnz ◽  
...  
Keyword(s):  
Climate Change ◽  
Community Structure ◽  
Community Composition ◽  
Environmental Conditions ◽  
Deep Sea ◽  
Gulf Of California ◽  
Fish Community ◽  
Demersal Fish ◽  
Fish Community Structure ◽  
Explained Variance

Natural gradient systems can be used to examine the vulnerability of deep-sea communities to climate change. The Gulf of California presents an ideal system for examining relationships between faunal patterns and environmental conditions of deep-sea communities because deep-sea conditions change from warm and oxygen-rich in the north to cold and severely hypoxic in the south. The Monterey Bay Aquarium Research Institute (MBARI) remotely operated vehicle (ROV) ‘Doc Ricketts’ was used to conduct seafloor video transects at depths of ~200-1400 m in the northern, central, and southern Gulf. The community composition, density, and diversity of demersal fish assemblages were compared to environmental conditions. We tested the hypothesis that climate-relevant variables (temperature, oxygen, and primary production) have more explanatory power than static variables (latitude, depth, and benthic substrate) in explaining variation in fish community structure. Temperature best explained variance in density, while oxygen best explained variance in diversity and community composition. Both density and diversity declined with decreasing oxygen, but diversity declined at a higher oxygen threshold (~7 µmol kg-1). Remarkably, high-density fish communities were observed living under suboxic conditions (<5 µmol kg-1). Using an Earth systems global climate model forced under an RCP8.5 scenario, we found that by 2081-2100, the entire Gulf of California seafloor is expected to experience a mean temperature increase of 1.08 ± 1.07°C and modest deoxygenation. The projected changes in temperature and oxygen are expected to be accompanied by reduced diversity and related changes in deep-sea demersal fish communities.

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.

A new apparatus for the direct measurement of otter trawling effects on the epibenthic and hyperbenthic macrofauna

2003 ◽  
Vol 83 (6) ◽  
pp. 1363-1368 ◽  
Author(s):  
P.T. Koulouri ◽  
C.G. Dounas ◽  
A.S. Eleftheriou
Keyword(s):  
Continental Shelf ◽  
Mechanical System ◽  
Direct Measurement ◽  
Eastern Mediterranean ◽  
Otter Trawl ◽  
Continuous Record ◽  
New Apparatus ◽  
Surface Vessel

A towed trawl simulator sledge (TTSS2) for collecting quantitatively small macrobenthic animals disturbed by the passage of otter trawl groundrope typical of the local fishery is described and illustrated. The TTSS2 was towed from a surface vessel at a speed within the range of commercial trawls, incorporating three sampling nets that open and close by means of an electro-mechanical system. An odometer in contact with the seabed provided a continuous record of the trawled ground. The degree of efficiency of the TTSS2—by means of the attached groundrope that stirs up the surface of the bottom ahead of the nets—was tested in the northern continental shelf of Crete (eastern Mediterranean). Additional trials with a much heavier groundrope were also performed. Analysis and comparison of TTSS2 samples with endobenthic, hyperbenthic and planktonic samples collected by means of conventional sampling gears indicate the presence of a well-defined and distinct fauna in the plume of resuspended sediment behind the groundrope.

scholarly journals Use of avoidance behaviours to reduce the economic impacts of the EU Landing Obligation: the case study of a mixed trawl fishery

2019 ◽  
Vol 76 (6) ◽  
pp. 1554-1566
Author(s):  
Fabien Pointin ◽  
Fabienne Daurès ◽  
Marie-Joëlle Rochet
Keyword(s):  
Temporal Distribution ◽  
Grid Method ◽  
Fishing Effort ◽  
Economic Losses ◽  
Otter Trawl ◽  
Trawl Fishery ◽  
Nested Grid ◽  
Fishing Practices ◽  
The Eu

Abstract The EU Landing Obligation (LO) is designed to reduce bycatch (i.e. unwanted catch) through more selective fishing practices, such as avoidance behaviours which consist in allocating fishing effort to other species, fishing grounds or seasons. Incentives for fishers to change their behaviours depend on their economic performances as well as their ability to avoid bycatch. Changes in economic performances under the LO are evaluated based on cost and revenue equations. The nested grid method is then used to explore the spatial and temporal distribution of landings and discards, and to suggest alternative effort allocation to avoid bycatch. This article is focussed specifically on the French otter trawl fishery in the eastern English Channel and southern North Sea. Results suggest that under the LO the choke species problem will curtail fishing activities earlier in the year, leading to significant economic losses. In the absence of significant quota top-ups (at least 75%), a change in fishing practices consisting in reducing overall bycatch by 30% is insufficient to reduce losses. With a particular attention to choke species, more economically efficient avoidance strategies can be found thanks to the nested grid method.

Trophic ecology of the chihuil sea catfish (Bagre panamensis) in the south-east Gulf of California, México

2017 ◽  
Vol 98 (4) ◽  
pp. 885-893 ◽  
Author(s):  
Víctor M. Muro-Torres ◽  
Felipe Amezcua ◽  
Raul E. Lara-Mendoza ◽  
John T. Buszkiewicz ◽  
Felipe Amezcua-Linares
Keyword(s):  
Gulf Of California ◽  
Trophic Ecology ◽  
Trophic Position ◽  
Feeding Habits ◽  
Isotope Analysis ◽  
Demersal Fish ◽  
Trophic Levels ◽  
High Plasticity ◽  
Combined Use ◽  
Ecosystem Based Fisheries Management

The trophic ecology of the chihuil sea catfish Bagre panamensis was studied through high-resolution variations in its feeding habits and trophic position (TP) in the SE Gulf of California, relevant to sex, size and season. The combined use of stomach content (SCA) and stable isotope analysis (SIA) allowed us to perform these analyses and also estimate the TP of its preys. Results of this study show that the chihuil sea catfish is a generalist and opportunistic omnivore predator that consumes primarily demersal fish and peneid shrimps. Its diet did not vary with climatic season (rainy or dry), size or sex. Results from the SIA indicated high plasticity in habitat use and prey species. The estimated TP value was 4.19, which indicates a tertiary consumer from the soft bottom demersal community in the SE Gulf of California, preying on lower trophic levels, which aids in understanding the species' trophic role in the food web. Because this species and its prey are important to artisanal and industrial fisheries in the Gulf of California, diet assimilation information is useful for the potential establishment of an ecosystem-based fisheries management in the area.

Sign in / Sign up

Export Citation Format

Share Document