The biology of the squid Loligo vulgaris in relation to the artisanal fishing site of Tifnit, Morocco.

Abstract

The fishery and the biology of the inshore squid Loligo vulgaris were studied at the artisanal fishery of Tifnit from May 1985 to April 1986. The total landing in the area was 96 tons, with a local sale value of 2,113,510 dirhams. Dories using trammel nets landed 67% of the catch which accounted for 55% of the total sale value. The remaining catch was landed by dories using jigs and hooks. The life cycle of Loligo vulgaris was studied during the fishing season from samples taken randomly three times per week. The growth study was done using length-frequency data for 21,409 squid. Growth rates comparisons showed that males grew in length faster than females (t-test; P $<$ 0.05). However, females were heavier than males at a similar length above 100 mm (P $<$ 0.05). Life span was estimated as 2.5 years for females and nearly 4 years for males. Females outnumbered males throughout the year. The squid spawned throughout the year. Fresh eggs were collected from sand and silt bottoms and at depths ranging from 6 to 120 m. First size at maturity was estimated as 155 mm for males and 180 mm for females. Maximum fecundity was estimated as 42,000 eggs. This estimate was derived from counts of eggs contained both in the ovary and in the internal oviduct. Food habit studies showed that Loligo fed mainly on fishes, crustaceans and squid of its own species (cannibalism). The estimated exploitation rate indicated that the stock was underfished. The monthly fishing mortality rate that would maximize the yield was estimated as 5 times greater than the actual rate.