Population biology and status of exploitation of introduced garfishBelone belone euxini(Günther, 1866) in the Black Sea

Abstract

The garfish Belone belone euxini (Gu¨nther, 1866) is a commercially important pelagic fish species in Sinop artisanal fishery, which is showing a decreasing trend in catch results. As a basis for fisheries management a sampling program was carried out between October 2000 and September 2001 along the Turkish coast of the Black Sea, to study the population structure, growth, and reproduction cycle of garfish in the area, and to achieve a rough estimate of exploitation. The length-weight relationship and von Bertalanffy growth parameters were estimated as W ¼ 0.00076 L 3.137 , L ¥ ¼ 74.64 cm, K ¼ 0.13 year )1 , t o ¼ )3.67, respectively. First sexual maturity was estimated at age 2 and at a total length of 38.8 cm for females. The spawning period was from May to September. The total fecundity-length relationship was estimated as F ¼ 0.0041 L 4.1086 (r 2 ¼ 0.92). Mortality rates were Z ¼ 1.24 year )1 , M ¼ 0.23 year )1 and F ¼ 1.01 year )1 for total, natural, and fishing mortality, respectively. The exploitation ratio E ¼ 0.81 indicates that the population is heavily exploited.

The reproductive cycle, size at maturity and fecundity of garfish (Belone belone, L. 1761) in the eastern Adriatic Sea

“…In comparison with the previous studies (Yüce 1970;Bedoui et al 2002;Fehri-Bedoui and Gharbi 2004;Sinovčić et al 2004;Uçkun et al 2004;Samsun et al 2006), the length range of Fig. 7 Images of garfish gonad tissue: a ripe female (marked oocytes of three different development stages were v-maturing oocytes or oocytes in the stage of vitellogenesis in which the yolk granules that appeared first in the periphery of the cytoplasm increased in size and number dispersing within the cytoplasm, mn-ripe oocytes in which the fusion of several oil droplets resulted in the formation of a large oil droplet, which migrated towards animal pole together with the nucleus and hy-''hydrated oocyte'' in which the yolk granules fused forming a continuous mass of fluid yolk and with its formation the spawning is initiated), b ripe male (marked cells were SPSpermatocytes-small oval cells; ST-Spermatids-cells with larger and rounded nucleus and SZ-Spermatozoa-the cells developed from spermatids when they were rejected into the cyst cavity as the spermatogenesis was coming to an end) garfish specimens in the present study is the widest reported till now for garfish specimens inhabiting the Adriatic Sea, Mediterranean and Black Sea.…”

“…That was also confirmed by the obtained regression equation between ovarian weight and the total garfish weight during the spawning season (Wg = 0.112 W-0.692; r = 0.821). An exponential relationship between absolute fecundity and total body length of garfish was also approved by Samsun et al (2006). Dorman (1991) attained linear relationship between batch fecundity and the total body length for garfish inhabiting the Atlantic.…”

“…Fecundity A paper published earlier on fecundity of this species carried out quite similar values of absolute fecundity. Thus, Yüce (1970) reported the range of absolute fecundity 10,196-48,903 oocytes per ovary, while Samsun et al (2006) estimated the average absolute fecundity of 24,088 oocytes per garfish ovary. Range values of garfish batch fecundity were given by Dorman (1991) who reported the range of 2,193-10,804 hydrated oocytes per ovary; then, Uçkun et al (2004) estimated the range between 1,066 and 20,446 hydrated oocytes per ovary.…”

“…A few studies concerning some aspects of the reproductive biology of garfish were carried out for populations that inhabited the north-eastern Atlantic (Dorman 1989(Dorman , 1991, the Black Sea (Samsun et al 2006) and Aegean Sea (Uçkun et al 2004). The present study was undertaken to investigate reproductive traits like sex ratio, size at sexual maturity, spawning period and fecundity of garfish distributed in the Adriatic Sea.…”

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“…Spawning time based on gonadosomatic index and fecundity of B. belone was studied in the Turkey's Aegean Sea coasts by Uçkun et al (2004) and in the Bosporus by Yüce (1975). Moreover, only one study of B. euxini spawning time and absolute fecundity features was carried out for population in the middle Black Sea (Samsun et al, 2006). However, no knowledge existed on size at first maturity of B. euxini in the Black Sea.…”