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Diel variation in the catchability of rose shrimp, Parapenaeus longirostris, and associated species from a bottom trawl survey off the portuguese south coast
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Resumo(s)
An experimental crustacean bottom trawling survey targeting the deep-water rose shrimp
Parapenaeus longirostris was carried out off the south of Portugal over five 24-hour cycles.
Although circadian bias in the catch rates for this fishery has been reported, no conclusive
study had been carried out until now. Catch per unit effort oscillated with the time of the
day. Total catches, both in numbers and weight considerably higher in daytime than at
night, suggesting that the 24-hour light cycle strongly influences catchability of rose
shrimp. The rose shrimp, shows a clear shift in abundance from daytime to night hours,
with catches decreasing sharply at dusk and, then increasing significantly at dawn.
Overall, the most captured fish species: european hake, Merluccius merluccius; monkfish,
Lophius budegassa; european conger, Conger conger; and great forkbeard, Phycis
blennoides; present the same trend, although less marked. The exceptions are: silver
scabbardfish, Lepidopus caudatus; blue Whiting, Micromesistius poutassou; tongue sole,
Symphurus nigrescens; atlantic mackarel Scomber scombrus and silver cod, Gadiculus
argenteus; whose catches were higher in the night hours. Understanding, the circadian
variability in catches of highly valuable commercial species such as the deep-water rose
shrimp may contribute to an improved management, by allowing a better control of fishing
effort and more efficient use of technical measures
Descrição
Dissertação de mest., Aquacultura e Pescas, Faculdade de Ciências e Tecnologia, Univ. do Algarve, 2011
Palavras-chave
Catchability Circadian variability Deep-water rose shrimp Bottom trawling Portugal