Tahong Shells as Additive in Tile Making

Fisheries Research 101 (2010) 100–107

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Fisheries Research

journal homepage: www.elsevier.com/locate/fishres

Estimation of basket trap selectivity for changeable nassa (Nassarius mutabilis) in the Adriatic Sea

Fabio Grati ∗ , Piero Polidori, Giuseppe Scarcella, Gianna Fabi

Istituto di Scienze Marine, Consiglio Nazionale delle Ricerche, Largo Fiera della Pesca 2, 60125 Ancona, Italy

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Size selectivity of basket traps for changeable nassa (Nassarius mutabilis) was estimated through comparative fishing trials with traps varying in mesh size and net colour. Selectivity curves of two commercial (19 mm white twine and 19 mm black twine) and three experimental (23, 26 and 28 mm white twine) traps were estimated using SELECT method. In addition, theoretical size-selectivity curves were calculated from morphometric data using a simplified version of Sechin method. Differing from the opinion of fishermen, N. mutabilis did not show any preference for dark coloured twine. Retention curves estimated with SELECT method had a very sharp selectivity and well fitted catch data in all cases. Theoretical size-selectivity curves were very close to size-selectivity curves obtained from experimental data. The two types of curve were very similar in shape, although the theoretical ones were shifted towards larger size classes and showed a slightly steeper slope than SELECT curves. The mesh size commonly used by fishermen is not adequate for rationally exploiting the resource, as catches mainly included undersized specimens, whilst the 23 and 26 mm mesh sizes would represent a good compromise between reduced occurrence of undersized individuals and satisfactory yields of commercial product. © 2009 Elsevier B.V. All rights reserved.

Article history: Received 16 June 2009 Received in revised form 21 September 2009 Accepted 21 September 2009 Keywords: Adriatic Sea Basket trap Nassarius mutabilis...