The biology of the giant red shrimp ( Aristaeomorpha foliacea) at an unexploited fishing ground in the Greek Ionian Sea

Abstract

Experimental trawl sampling was carried out along the Greek coast of the Ionian Sea between January and December 1997 at three depth zones: >500, 500–600 and <600 m, to study the distribution and population structure of an unexploited stock of the giant red shrimp ( Aristaeomorpha foliacea). The overall length–frequency distribution ranged between 16 and 62 mm (carapace length, CL), while the most abundant classes were between 40 and 48 mm CL. Length–frequency distribution was significantly dependent on depth. Medium-sized adults appeared in the shallower zone (>500 m), the young-of-the-year in the middle (500–600 m) and larger adults in the deepest (<600 m). The highest abundance was observed in the 500–600 m depth zone. Growth analysis indicated that the population was composed of two to three annual cohorts. The VBGF parameters were CL ∞=47.2 mm, K=0.564 per year, t 0=−0.13 years and CL ∞=64.086 mm, K=0.460 per year, t 0=−0.192 years for males and females, respectively. The asymptotic weight estimated from length–weight relationships was 32.6 and 67.3 g for males and females, respectively. The reproductive period, estimated from the maturity stages of females, is from summer to early autumn with a peak from June to August. The smallest mature female was 37.5 mm CL. Sex ratio was significantly higher than 1:1 in favor of males and no correlation with depth was found. Natural mortality was estimated at 0.57–0.66 and 0.47–0.55 per year for males and females, respectively. Total mortality was 0.58–0.62 and 0.53–0.62 per year for males and females, respectively. The abundance and the population dynamics of this species suggest that the population of the giant red shrimp in the Ionian Sea could provide a new target species to the deep-trawl fishery of the area.