Mono- vs multifilament gillnets: effects on selectivity of narrow-barred Spanish mackerel Scomberomorus commerson in the Persian Gulf

Iranian coastal fishers targeting narrow-barred Spanish mackerel ( Scomberomorus commerson ) recently replaced their historical multifilament gillnets with those made from monofilament, evoking management concerns over potential increases in catch-per-unit-of-effort. During 20 fishing days, we compa...

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Bibliographic Details
Published in:Journal of the Marine Biological Association of the United Kingdom 2020-03, Vol.100 (2), p.285-290
Main Authors: Eighani, Morteza, Bayse, Shannon M., Paighambari, Seyed Yousef, Broadhurst, Matt K.
Format: Article
Language:English
Subjects:
Catch per unit effort
Catfish
Confidence intervals
Deployment
Endangered & extinct species
Fishers
Fishing
Fishing nets
Freshwater fishes
Gillnets
Mackerel
Marine biology
Marine fishes
Scomberomorus commerson
Selectivity
Species
Stocks
Teeth
Yarns
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Summary:Iranian coastal fishers targeting narrow-barred Spanish mackerel ( Scomberomorus commerson ) recently replaced their historical multifilament gillnets with those made from monofilament, evoking management concerns over potential increases in catch-per-unit-of-effort. During 20 fishing days, we compared catches from replicate surface-set gillnets that were identical in terms of mesh size (140 mm stretched opening), length (180 m), depth (30 m), hanging ratio (0.56) and spatio-temporal deployment, but had different materials: multifilament (1.8-mm diameter twisted twine) vs monofilament (0.8-mm diameter twine). Compared with the multifilament gillnet, there was a trend of greater catches (up to 1.3×) of S. commerson and another retained species, mackerel tuna ( Euthnus affinis ), along with one discarded species, giant catfish ( Netuma thalassina ) by the monofilament gillnet. However, statistical significance was restricted to E. affinis catches and a bias towards smaller S. commerson. These differences were attributed to species-specific catching mechanisms within gillnet material, with larger S. commerson retained by their teeth in the multifilament and all E. affinis more securely retained by their deeper bodies in the monofilament. Gillnet materials require regulation to preclude excessive effort on fully exploited stocks of species such as S. commerson.
ISSN:0025-3154
1469-7769
DOI:10.1017/S0025315419001243