Fishing-in-balance, mean trophic level, ratio of pelagic and demersal fish landings and piscivory indices of coastal fisheries landings in Iranian part of the Caspian Sea

Abstract

This study aimed to investigate the impact of fishing in Iranian part of the Caspian Sea during 1991-2017 years using fishing-in-balance (FiB), mean trophic level (MTI), ratio of pelagic and demersal fish landings (P/D) and piscivory (PI) indices. The mean (±S.D) of MTI were 2.91±0.38 (95% C.I =3.14-2.67). Its value is first reduced and then increase happened and ultimately stays constant. The mean of FiB was 0.13 (95% C.I=0.28-(-0.02)) and its trend was similar to that of total landing. The mean of Pi index, P/D index, pelagic fish and demersal fish were 0.04±0.02 (95% C.I=0.09-(-0.012)), 3.16±2.31 (95% C.I = 0.6-(-0.52)), 38529±22883 (95% C.I=38585-38472) and 13380±3314 (95% C.I= 3401-13358), respectively. The results revealed that the fish stock in the Iranian waters of the Caspian Sea have been over-exploited. Considering that fishing impacts on the trophic level, we suggest that the fishery management should not continue this trend.