scholarly journals Assessment of the relative catch performance of hake, red mullet and striped red mullet in a modified trawl extension with T90 netting

2018 ◽  
Vol 82 (S1) ◽  
pp. 19 ◽  
Author(s):  
Iván Sola ◽  
Francesc Maynou
Keyword(s):  
Target Species ◽  
Commercial Catch ◽  
Red Mullet ◽  
Comparison Approach ◽  
Commercial Species ◽  
Nw Mediterranean ◽  
Catch Rates ◽  
Trawl Fisheries ◽  
Discernible Difference ◽  
European Hake

We studied the relative catch performance of a modified trawl fitted with an extension piece using a 90º turned mesh (T90) in comparison with a standard trawl net used in NW Mediterranean bottom trawl fisheries employing a diamond mesh net. The comparison was made by means of paired experimental hauls using the same fishing vessel with alternate deployments of the standard net (control) and the experimental net. We used the catch comparison approach for three target species of the fishery: European hake, red mullet and striped red mullet. Our results show that the experimental net significantly reduces the catches of small-size hake and red mullet (though there was no discernible difference for striped red mullet), reducing unwanted catches of regulated species under the Landings Obligation. The overall catch rates of hake, pooled over all sizes, also increased by an estimated 50%, while the catch rates of red mullet and striped red mullet were significantly lower. However, considering all commercial species, the experimental net produced losses of commercial catch and income estimated at 17% and 18%, respectively, which may pose a barrier to the adoption of this relatively simple, inexpensive solution.

scholarly journals Bioeconomic analysis of the effects of modifying the trawl extension piece with T90 netting

2018 ◽  
Vol 82 (S1) ◽  
pp. 27 ◽  
Author(s):  
Iván Sola ◽  
Francesc Maynou
Keyword(s):  
Economic Impact ◽  
Transition Period ◽  
Bottom Trawl ◽  
Fishing Mortality ◽  
Target Species ◽  
Commercial Use ◽  
Red Mullet ◽  
Nw Mediterranean

We assessed the effect of the European discards ban on the profitability of bottom trawlers in a case study fishery (GSA06, NW Mediterranean) in the transition period 2017-2018, when the species that characterize the fishery, viz. hake and red mullet, fall under the discards ban. We used the results of Sola and Maynou (2018) to simulate the adoption of a modified bottom trawl design using a T90 extension net to reduce the catches of undersize hake and red mullet. Our results show that the economic impact of the former discards brought to land on the fisheries operators is expected to be low, regardless of the possible commercial use of these unwanted catches. Furthermore, the adoption of a more selective bottom trawl design would increase the escape of undersize individuals and likely reduce fishing mortality of the target species, contributing to stock rebuilding and providing higher income to the fisheries operators in the medium to long term.

scholarly journals Towards more selective Mediterranean trawl fisheries: are juveniles and trash excluder devices effective tools for reducing undersized catches?

2018 ◽  
Vol 82 (S1) ◽  
pp. 215 ◽  
Author(s):  
Sergio Vitale ◽  
Giacomo Milisenda ◽  
Michele Gristina ◽  
Pasquale Baiata ◽  
Sara Bonanomi ◽  
...  
Keyword(s):  
Ad Hoc ◽  
Fishing Effort ◽  
Bottom Trawl ◽  
Steel Bars ◽  
Generalized Additive Mixed Models ◽  
Commercial Species ◽  
Additive Mixed Models ◽  
Sorting Efficiency ◽  
Trawl Fisheries ◽  
European Hake

Mediterranean trawl fisheries are characterized by a critical combination of high fishing effort and low size at first capture for most commercial species. In this study we tested the use of sorting grids installed on bottom trawl nets to minimize the catch of undersized deep-water rose shrimp (Parapenaeus longirostris, DPS) and European hake (Merluccius merluccius, HKE). The catch of a traditional trawl net was compared with that obtained with the same net equipped with ad hoc designed juveniles and trash excluder devices (JTEDs) during an experimental survey. Three different JTEDs were tested: the first (G1-SM40) was built with a net of 40-mm square mesh; the second (G2-ST20) and third (G3-ST25) with vertical steel bars spaced 20 and 25 mm, respectively. The probability of retaining DPS and HKE by length class in trawl nets with and without JTED was analysed using generalized additive mixed models. With G1-SM40, the reduction of undersized individuals in the cod-end was about 60% and 44% for DPS and HKE, respectively. With G2-ST20, a 34% catch decrease of HKE individuals smaller than 20 cm total length was observed. A loss of marketable fractions of DPS was recorded with G1-SM40 (–25%) and G2-ST20 (30%). Finally, JTD G3-ST25 was efficient at reducing the catch of undersized specimens of DPS and HKE, but showed a higher loss of marketable fractions than the other JTEDs. Although further fishing trials would be required to maximize the sorting efficiency of the grids, the results obtained clearly indicated that grids can substantially reduce unwanted catches of undersized DPS and HKE in Mediterranean bottom trawl fisheries.

Community-level impacts of trawl selectivity in the Eastern Mediterranean Sea assessed using an ecosystem modelling approach

2020 ◽  
Author(s):  
İsmet Saygu ◽  
Johanna J Heymans ◽  
Clive Fox ◽  
Hüseyin Özbilgin ◽  
Jacob W Bentley ◽  
...  
Keyword(s):  
Impact Analysis ◽  
Positive Impact ◽  
Eastern Mediterranean ◽  
Dynamic Simulations ◽  
Red Mullet ◽  
Ecopath Model ◽  
Commercial Species ◽  
The Mediterranean ◽  
Trophic Impact ◽  
Trawl Fisheries

Abstract Switching from the traditional 40- or 44-mm diamond mesh codends to 50-mm diamond mesh (D50) or 40-mm square mesh (S40) codends is known to improve the size selection for commercial species and reduce discarding in the Mediterranean demersal trawl fisheries. This change has been recommended in the General Fisheries Commission for the Mediterranean and European Commission regulations. However, ecosystem-based assessment of improved selectivity still remains a challenge, and that is the aim of this study. For this purpose, an Ecopath model was developed and used to initialize dynamic simulations in Ecosim. The simulations changed gear-specific fishing mortality rates to represent the shifting from traditional codend to alternative codends. Our results suggest that the use of D50 or S40 codends would have a positive impact on the ecosystem as a whole and on the stock status of several commercial and non-commercial groups. Mixed trophic impact analysis indicated that, for species, like red mullet, the S40 codend was significantly better than the D50 codend. This information can be useful to policymakers, particularly for the areas where red mullet is the main target species and could inform trawl mesh options in the eastern Mediterranean.

scholarly journals Round scallops and square meshes: a comparison of four codend types on the catch rates of target species and by-catch in the Queensland (Australia) saucer scallop (Amusium balloti) trawl fishery

2008 ◽  
Vol 59 (10) ◽  
pp. 849 ◽  
Author(s):  
Anthony J. Courtney ◽  
Matthew J. Campbell ◽  
Darren P. Roy ◽  
Mark L. Tonks ◽  
Keith E. Chilcott ◽  
...  
Keyword(s):  
Sea Urchins ◽  
Catch Rate ◽  
Target Species ◽  
Bivalve Molluscs ◽  
Sea Stars ◽  
Incidental Capture ◽  
Trawl Fishery ◽  
By Catch ◽  
Catch Rates ◽  
Trawl Fisheries

Concern over the amount of by-catch from benthic trawl fisheries and research into the problem have increased in recent years. The present paper demonstrated that by-catch rates in the Queensland (Australia) saucer scallop (Amusium balloti) trawl fishery can be reduced by 77% (by weight) using nets fitted with a turtle excluder device (TED) and a square-mesh codend, compared with a standard diamond-mesh codend with no TED. This large reduction was achieved with no significant effect on the legal size scallop catch rate and 39% fewer undersize scallops were caught. In total, 382 taxa were recorded in the by-catch, which was dominated by sponges, portunid crabs, small demersal and benthic fish (e.g. leatherjackets, stingerfish, bearded ghouls, nemipterids, longspine emperors, lizard fish, triggerfish, flounders and rabbitfish), elasmobranchs (e.g. mainly rays) and invertebrates (e.g. sea stars, sea urchins, sea cucumbers and bivalve molluscs). Extremely high reductions in catch rate (i.e. ≥85%) were demonstrated for several by-catch species owing to the square-mesh codend. Square-mesh codends show potential as a means of greatly reducing by-catch and lowering the incidental capture and mortality of undersize scallops and Moreton Bay bugs (Thenus australiensis) in this fishery.

Main drivers of spatial change in the biomass of commercial species between summer and winter in the NW Mediterranean Sea

2020 ◽  
pp. 105227
Author(s):  
Elena Lloret-Lloret ◽  
Maria Grazia Pennino ◽  
Daniel Vilas ◽  
José María Bellido ◽  
Joan Navarro ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Spatial Change ◽  
Commercial Species ◽  
Nw Mediterranean ◽  
Nw Mediterranean Sea

Fish and invertebrate by-catch in the crab pot fishery in the Isle of Man, Irish Sea

2017 ◽  
Vol 98 (8) ◽  
pp. 2099-2111
Author(s):  
Fikret Öndes ◽  
Michel J. Kaiser ◽  
Lee G. Murray
Keyword(s):  
Irish Sea ◽  
Target Species ◽  
Catch Per Unit Effort ◽  
Isle Of Man ◽  
Ecosystem Effects ◽  
By Catch ◽  
Catch Rates ◽  
Taxonomic Groups ◽  
Catch Composition ◽  
Autumn And Winter

Baited trap or pot fisheries are considered to have relatively few wider ecosystem effects on the marine environment, particularly when compared with towed mobile fishing gear. However, this assumption is rarely tested in the field. This study aimed to determine the composition of non-target species that occur in crustacean pots and to assess spatial and temporal differences in catches in the waters around the Isle of Man, Irish Sea. The data were collected using fishery independent surveys and a questionnaire study. Based on fishery independent surveys, a total of five taxonomic groups and 43 species occurred as by-catch. The dominant by-catch species was velvet crab Necora puber. The by-catch per unit effort (BPUE) for all of the non-target species was low particularly in comparison to towed bottom gear fisheries around the Isle of Man. BPUE of species composition varied considerably between different locations around the Isle of Man. The results of both the fishery independent and questionnaire data suggested that the by-catch rates varied with season with peak BPUE occurring in spring which then declined into autumn and winter. By-catch composition did not decrease significantly with an increasing target species catch. Overall, by-catch was low relative to target species catch which may be partially attributable to the use of escape panels in pot fisheries in the Isle of Man.

scholarly journals Female reproductive biology and spawning periodicity of two species of king prawns, Penaeus longistylus Kubo and Penaeus latisulcatus Kishinouye, form Queensland's East Coast Fishery

1988 ◽  
Vol 39 (6) ◽  
pp. 729 ◽  
Author(s):  
AJ Courtney ◽  
MCL Dredge
Keyword(s):  
Egg Production ◽  
East Coast ◽  
Sea Water ◽  
Coastal Region ◽  
Ovary Development ◽  
Commercial Catch ◽  
Ovary Weight ◽  
Species Population ◽  
Spawning Periodicity ◽  
Catch Rates

In the coastal region of central Queensland female red-spot king prawns, P. longistylus, and the western or blue-leg king prawns, P. latisulcatus, had high mean ovary weights and high proportions of advanced ovary development during the winter months of July and August of 1985 and 1986. On the basis of insemination, both species began copulating at the size of 26-27 mm CL, but P. longistylus matured and spawned at a smaller size than P. latisulcatus. Abundance of P. longistylus was generally three to four times greater than that of P. latisulcatus but the latter was subject to greater variation in abundance. Low mean ovary weight and low proportions of females with advanced ovaries were associated with the maximum mean bottom sea-water temperature (28.5�C) for both species. Population fecundity indices indicated that peaks in yolk or egg production (a) displayed a similar pattern for both species, (b) varied in timing from year to year for both species and (c) were strongly influenced by abundance. Generally, sample estimates of abundance and commercial catch rates (CPUE) showed similar trends. Differences between the two may have been due to changes in targeted commercial effort in this multi-species fishery.

European hake (Merluccius merluccius, Linnaeus 1758) spillover analysis using VMS and landings data in a no-take zone in the northern Catalan coast (NW Mediterranean)

2021 ◽  
Vol 237 ◽  
pp. 105870 ◽  
Author(s):  
Joan Sala-Coromina ◽  
Jose Antonio García ◽  
Paloma Martín ◽  
Ulla Fernandez-Arcaya ◽  
Laura Recasens
Keyword(s):  
Merluccius Merluccius ◽  
Catalan Coast ◽  
Nw Mediterranean ◽  
European Hake

Validity of using translucent zones of otoliths to age the pilchard Sardinops sagax neopilchardus from Albany, Western Australia

1996 ◽  
Vol 47 (4) ◽  
pp. 617 ◽  
Author(s):  
WJ Fletcher ◽  
SJ Blight
Keyword(s):  
Western Australia ◽  
Age Groups ◽  
Growth Curves ◽  
Relative Number ◽  
Older Individuals ◽  
Commercial Catch ◽  
Monthly Basis ◽  
Lower Accuracy ◽  
Sardinops Sagax ◽  
Catch Rates

Otoliths (sagittae) of the pilchard (Sardinops sagax neopilchardus) from the Albany region of Western Australia were examined on a monthly basis during 1989 to 1991. When read consecutively, with the month of capture known, a clear annual cycle of an increase in marginal increments to October followed by a decline was recorded. This pattern was, however, severely distorted when samples were re-examined after having been jumbled and the month of capture concealed. Younger age groups (≤3) showed evidence of multiple rings being formed annually, but not in all years or individuals, and this was not evident in older individuals (≥4). Agreement between readings was low (43-53%), especially between different readers. Resultant growth curves showed that males grow to a smaller size (L∞ =164, K = 0.805, Φ = 1.03) than females (L∞ = 174, K = 0.584, Φ= 0.95). Agreement between counts of annuli and ages estimated by using otolith weight and length was only 54% for all individuals, but increased to 76% for individuals assigned the same age by different readers. Given the poorer predictions of future catch rates from the relative number of 2-year-olds in the commercial catch using annuli (implying lower accuracy) and increased complexity in preparation, otolith weights will be the method adopted for future ageing.

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