Further evidence of spawning of bluefin tuna (Thunnus thynnus L., 1758) and the tuna species (Auxis rochei Ris., 1810, Euthynnus alletteratus Raf., 1810) in the eastern Mediterranean Sea: preliminary results of TUNALEV larval survey in 2004 Summary A tuna larval survey (TUNALEV) in the Northern Levantine Basin (Cilician Basin) was conducted onboard a trawler from 5 to 18 June 2004. To determine the spatial distribution and abundance of tuna larvae, Bongo 60 and Bongo 90 nets were used. Ichtyoplankton samples from 104 stations were taken. In total, 121 bluefin tuna (Thunnus thynnus), 94 bullet tuna (Auxis rochei) and 22 Atlantic black skipjack (Euthynnus alletteratus) larvae were collected. In comparison with the other tuna larvae, the concentration of bluefin tuna larvae was highest in the Bay of Mersin. The collected larvae in this area were composed mainly of 5-9 mm size specimens.

Fishing trials were carried out with gill nets and trammel nets in the northern aegean Sea from March 2004 to February 2005. Four different mesh sizes for the gill nets and the inner panel of trammel nets (16, 18, 20 and 22 mm bar length) were used. Selectivity parameters for the five most economically important species, bogue (Boops boops), annular sea bream (Diplodus annularis), striped red mullet (Mullus surmuletus), axillary sea bream (Pagellus acarne) and blotched picarel (Spicara maena), caught by the two gears were estimated. the SeLeCt method was used to estimate the selectivity parameters of a variety of models. Catch composition and catch proportion of several species were different in gill and trammel nets. the length frequency distributions of the species caught by the two gears were significantly different. the bi-modal model selectivity curve gave the best fit for gill net and trammel net data, and there was little difference between the modal lengths of these nets. However, a clear difference was found in catching efficiency. the highest catch rates were obtained with the trammel net. Given that many discard species and small fish are caught by gill nets and trammel nets with a mesh size of 16 mm, it is clear that these nets are not appropriate for fisheries. Consequently, the best mesh size for multispecies fisheries is 18 mm. this mesh size will considerably reduce the numbers of small sized individuals and discard species in the catch.

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The common two-banded seabream Diplodus vulgaris and Diplodus sargus were sampled from non-commercial fishing catches around the Maltese Islands between July 2012 and December 2017. A total of 1550 (D. vulgaris N=1204, D. sargus N=346) specimens were collected. In this study, age, growth, length-weight relationship (LWR), condition factor (K) and relative condition factor (Kn) were investigated. Ages ranged from 0 to 17 years for D. sargus and 0 to 16 years for D. vulgaris. A positive allometric growth was observed for D. sargus while growth in D. vulgaris was isometric. Average Kn was found to be 0.99 and 1.01 in D. vulgaris and 0.97 and 1.00 in D. sargus for males and females respectively. The growth parameters of the von Bertalanffy equation were: L∞=26.71 and 30.86 cm, K= 0.275 and 0.286 year-1 and tₒ =-2.27 and-1.61 year for all individuals of D. vulgaris and D. sargus respectively. This study is the first reference on the LWR equation parameters, Kn, K and Age for these species around the Maltese Islands and establishes a new maximum age for D. vulgaris of 16 years.

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