Shrimp, Bycatch and Discard Composition of Fish Caught by Small-scale Shrimp Trawlers in the Hormuzgan Coast of Iran in the Persian Gulf
Shrimp trawl fisheries is a common source of livelihood in the Persian Gulf, but very little information is available about the species composition and length frequency of the large rates of bycatch caught in this region. This study determined the abundance of caught species and the length frequency of bycatch in small-scale shrimp trawl fisheries in the fishing grounds of Hormuzgan province, Iran, in the Persian Gulf. Samples were collected by bottom trawl net during the autumn of 2011. During the shrimp season, 41 hauls with a total catch of 6,482 kg were sampled. The catch composition included: 56 species from 34 teleostei families, 5 species from 4 elasmobranch families and 10 species from 6 invertebrate families. Total catch consisted of 70% bycatch, 24% shrimp and 6% commercial species. Bycatch-to-shrimp ratio was calculated as 3:1. One sample t-test found a significant difference (P<0.05) between mean length (Lmean) and length at maturity (Lm) for 16 non-commercial and 11 commercial species, while for 3 species (Leiognathus bindus, Acanthopagrus latus and Otolithes ruber), the difference was not significant. Lm value was significantly greater than Lmean for 21 out of the 30 species analyzed, indicating that young and immature fishes were harvested. There is a danger that too many fish may be caught before they could spawn and replace themselves. The results can be interpreted as an important tool in monitoring fishery and in the evaluation of any management measure. They can also be used to apprise fishers to reduce bycatch of vulnerable species.
Key Words: bycatch-to-shrimp ratio, catch per unit effort, Hormuzgan coasts, Lmean/Lm ratio, shrimp trawl fisherie