On the ecology of anchovy, Engraulis encrasicolus (L.) in the central Adriatic

Abstract

      Total length of anchovy from the Kaštela Bay, and Vis and Biševo Islands region caught during fishing season 1974 varied from 10.0 - 18.7 cm.

     Mean length of anchovy from the Vis and Biševo region (14.9 - 16.8 cm) exceeded that of anchovy from the Kaštela Bay (11.0 - 15.1 cm).

      Mean and modal lengths were consistently greater in females but they did not differ much from those of males.

      Sex ratio varied in the individual samples of catches from the Vis and Biševo region. The most aberrant sex ratio was that which showed 36% males and 64% females. In contrast, in the material as a whole the numbers of each sex were about equal, i. e. 46.7% males and 53.3% females.

      The spring is the period of an early maturation in anchovy and summer the peak in their sexual activity.

       During the period of the early maturation larger fish had more advanced state of gonads as well as higher values of gonad weight and gonosomatic ratio than smaller fish.

       First sexual maturity was recorded in male anchovy at a minimum total length 8.6 cm and in female fish at a minimum length 9.7 cm.

      Fluctuations in the anchovy mesenteric fat quantity were brought into connexion with the sexual cycle. The highest quantity of mesenteric fat was recorded during the inactivity period and the lowest during the peak in sexual activity. In March-May quantity of mesenteric fat was higher in larger fish than in smaller.

      Length exponent values in anchovy from Vis and Biševo Islands region were somewhat lower than those in anchovy from the Kaštela Bay. However, differences between the fish from the two regions appeared as to the size, gonad state, and the time of the year.

      Differences in length exponent values between male and female anchovy from Vis and Biševo Islands region were small whereas there was no difference at all between the ones from the Kaštela Bay.

      In the region of Vis and Biševo Islands, fish with the most advanced maturity stages showed somewhat lower length exponent values than all fish taken together.