Reproductive biology of ridgeback shrimp Solenocera choprai (Decapoda, Penaeoidea, Solenoceridae) off Mangalore coast, south India

Abstract:   The ridgeback shrimp Solenocera choprai has emerged as one of the important commercial species in 60–100 m depth zone off Karnataka coast, India, since 1993. Studies were conducted on S. choprai to understand its reproductive biology which can help in formulating policies for management of the species. The diagnostic features of reproductive morphology of the species were studied and illustrated in detail. Based on the coloration and size of the ovary and ova diameter variations, five stages of maturity in female S. choprai were identified. The mature ova are fully yolked with diameters between 0.24 and 0.35 mm. Size at maturity (50%) has been estimated at 54.5 and 66.5 mm total length (TL) in males and females, respectively. The gonadosomatic index (GSI) showed an increasing trend according to the advancement of maturity of the ovary, and monthly mean GSI showed a positive correlation with monthly percentage of spawners. Solenocera choprai was found to be a continuous breeder with two peaks: a major peak in November and another extended peak during January–February. The estimated numbers of ova in the mature ovary were 38 532 and 133 689 in shrimps measuring 80 and 110 mm TL, respectively. A sigmoidal increase in the female-to-male sex ratio with increase in size was noticed in the species. A χ ²-test showed that the annual distribution of females and males is not significantly different from a 1:1 ratio at the 1% level.     

东海凹管鞭虾的渔业生物学特性

根据1986-1990年和1997-2001年东海虾类资源调查及近年来监测调查的资料,对凹管鞭虾的渔业生物学特性进行了研究。结果表明,东海凹管鞭虾平均渔获率为562.3g.h-1,秋季最高达到1283.8g.h-1,主要分布在60m水深以东外海,盐度34以上,水温12~24℃海域,为高温高盐性虾类。雌虾周年平均体长和平均体重分别为76.0mm和7.0g;雄虾为72.8mm和5.5g,最大值出现在6-9月,最小值在2-4月。繁殖期在6-11月,高峰期在8-9月。周年出现两次快速生长期,第一次在8-11月,相对增长率雌虾为12.9%~11.2%,雄虾为7.9%~5.9%;第二次在翌年4-6月,雌、雄虾相对增长率为22.4%~13.4%和14.8%~14.1%。周年雌虾略多于雄虾,性比为1∶0.99。周年都摄食,摄食等级以1、2级为主,以夏季摄食量最高。     

东海中华管鞭虾种群动态及持续渔获量分析

中华管鞭虾为东海区桁杆拖虾和沿岸定置张网作业重要的渔获对象。本文根据2006-2008年桁杆拖虾监测调查数据整理的各月体长频率数据,应用FiSATⅡ软件分析结果表明：Von Bertalanff生长方程的参数K=1.2,极限体长L∞=112.88mm,t0=0.267;根据Pauly经验公式估算的自然死亡系数M=2.03606;由变换体长渔获曲线法估算的总死亡系数Z=4.71,利用率E=56.77%,开捕体长Lc=65.32mm;应用体长VPA方法估算的年平均资源量为47.74×10^9ind、2.58×10^4t。通过单位补充量产量、产值分析表明,该群体利用合理,开捕体长亦处最佳位置,若降低10%左右的捕捞努力量水平,既能使产值最大化（4.92亿元）,又能实现中华管鞭虾的可持续利用。