Detection and quantification of differences in catch rates among research vessel gears and commercial vessels

Delargy, Adam J.; Hold, Natalie; Heney, Charlotte; Cann, Ruth P.; Bhandari, Kiran; Colvin, Charlotte; Moore, Alec B. M.; Lincoln, Harriet; McCarthy, Ian; Hiddink, Jan Geert

doi:10.1016/j.fishres.2022.106371

Cited by 2 publications

(3 citation statements)

References 30 publications

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“…To compare size selectivity, we needed to estimate the skid dredge’s ability to retain scallops of a given size compared to the standard dredge [ 30 ]. We modelled the relative retention as a 4 th -order polynomial, and as a spline with five degrees of freedom using the ‘bs’ function in the ‘splines’ package [ 24 , 29 ].…”

Section: Methodsmentioning

confidence: 99%

Catch yield and selectivity of a modified scallop dredge to reduce seabed impact

Fenton,

Szostek,

Delargy

et al. 2024

PLoS ONE

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Global scallop fisheries are economically important but are associated with environmental impacts to seabed communities resulting from the direct physical contact of the fishing gear with the seabed. Gear modifications attempting to reduce this contact must be economically feasible such that the catch numbers for the target species is maintained or increased. This study investigated the outcome of reducing seabed contact on retained catch of scallops and bycatch by the addition of skids to the bottom of the collecting bag of scallop dredges. We used a paired control experimental design to investigate the impact of the gear modification in different habitat types. The modified skid dredge generally caught more marketable scallops per unit area fished compared with the standard dredge (+5%). However, the skid dredge also retained more bycatch (+11%) and more undersize scallops (+16%). The performance of the two dredges was habitat specific which indicates the importance of adjusting management measures in relation to habitat type. To realize the potential environmental benefits associated with the improvement in catchability of this gear modification, further gear modification is required to reduce the catch of undersize scallops and bycatch. Furthermore we advocate that technical gear innovations in scallop dredging need to be part of a comprehensive and effective fisheries management system.

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Section: Methodsmentioning

confidence: 99%

Catch yield and selectivity of a modified scallop dredge to reduce seabed impact

Fenton,

Szostek,

Delargy

et al. 2024

PLoS ONE

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show abstract

“…To make optimal use of data in Situation #1 (e.g., exploit the data collected with all research vessels instead of only the best-performing vessel) and Situation #2 (e.g., exploit bottom trawl and acoustic research survey data), fisheries scientists generally resort to "gear calibration" to account for differences in catchability across samples. Gear calibration can be performed via paired sampling in which samples are collected nearly simultaneously using different vessels, gears, or vessel-gear combinations to minimise spatio-temporal variations in catch rates between the vessels, gears, or vesselgear combinations (Miller 2013;Rademeyer and Butterworth 2013;Delargy et al 2022). Paired sampling allows for the calculation of fishing-power ratios (e.g., a catchability ratio between a new and old research vessel), which can be employed to calibrate the catches of the different vessels, gears, or vessel-gear combinations against one another so that they are comparable (Cadigan and Dowden 2010;Kotwicki et al 2017;Delargy et al 2022).…”

Section: Introductionmentioning

confidence: 99%

“…Gear calibration can be performed via paired sampling in which samples are collected nearly simultaneously using different vessels, gears, or vessel-gear combinations to minimise spatio-temporal variations in catch rates between the vessels, gears, or vesselgear combinations (Miller 2013;Rademeyer and Butterworth 2013;Delargy et al 2022). Paired sampling allows for the calculation of fishing-power ratios (e.g., a catchability ratio between a new and old research vessel), which can be employed to calibrate the catches of the different vessels, gears, or vessel-gear combinations against one another so that they are comparable (Cadigan and Dowden 2010;Kotwicki et al 2017;Delargy et al 2022). However, paired sampling is costly and often relies on the availability of several vessels.…”

Section: Introductionmentioning

confidence: 99%

Spatially varying catchability for integrating research survey data with other data sources: case studies involving observer samples, industry-cooperative surveys, and predators as samplers

Grüss

Thorson

Anderson

et al. 2023

Can. J. Fish. Aquat. Sci.

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Spatio-temporal models are widely applied to standardise research survey data and are increasingly used to generate density maps and indices from other data sources. We developed a spatio-temporal modelling framework that integrates research survey data (treated as a “reference dataset”) and other data sources (“non-reference datasets”) while estimating spatially varying catchability for the non-reference datasets. We demonstrated it using two case studies. The first involved bottom trawl survey and observer data for spiny dogfish (Squalus acanthias) on the Chatham Rise, New Zealand. The second involved cod predators as samplers of juvenile snow crab (Chionoecetes opilio) abundance, integrated with industry-cooperative surveys and a bottom trawl research survey in the eastern Bering Sea. Our integrated models leveraged the strengths of individual data sources (the quality of the reference dataset and the quantity of non-reference data), while downweighting the influence of the non-reference datasets via the estimated spatially varying catchabilities. They allowed for the generation of annual density maps for a longer time-period, and for the provision of one single index rather than multiple indices each covering a shorter time-period.

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Detection and quantification of differences in catch rates among research vessel gears and commercial vessels

Cited by 2 publications

References 30 publications

Catch yield and selectivity of a modified scallop dredge to reduce seabed impact

Catch yield and selectivity of a modified scallop dredge to reduce seabed impact

Spatially varying catchability for integrating research survey data with other data sources: case studies involving observer samples, industry-cooperative surveys, and predators as samplers

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