Gametogenic Cycle, the Spawning Season, First Sexual Maturity, and the Biological Minimum Size in Male Ruditapes philippinarum （Bivalvia： Veneridae） in Western Korea

The male gametogenic cycle, spawning season, first sexual maturity, and the biological minimum size in male Ruditapes philippinarum were investigated by qualitative and quantitative reproductive analyses. In the study of the male gametogenic cycle by qualitative histological analysis, the gametogenic cycle in male individuals can be classified into five successive stages： （1） early active stage, （2） late active stage, （3） ripe stage, （4） partially spawned stage, and （5） spent and inactive stage. Monthly changes in the gonad index in males measured by qualitative analysis showed a similar pattern to the male gametogenic cycle. In the study of the male gametogenic cycle by quantitative statistical analysis, monthly changes in the portions （%） of areas occupied by the testis areas to total tissue areas showed a rapid increase in March, and reached the maximum in May-June. And also monthly changes in the portions （%） of areas occupied by the spermatogenic stages to the testis area showed a maximum in May and gradually decreased from June to October. Therefore, this species showed a unimodal gametogenic cycle during the year, and the number of spawning seasons occurred once per year, from June to October, with a peak spawning between July and August. The percentage at the first sexual maturity of male clams ranging from 15.1-20.0 mm in shell length was 64.7%, and that of all individuals ranging from over 25.1 mm in shell length was 100%. The biological minimum size （shell lengths at 50% of sexual maturity （RMs0）） of male mature clams that was fitted to an exponential equation was 17.16 mm （considered to be 1 year old）. Because harvesting clams less than 17.16 mm in shell length could potentially cause a drastic reduction in recruitment, a measure indicating a prohibitory fishing size should be enacted for adequate fisheries management.

Breeding strategy of Acrossocheilus fasciatus in the Puxi Stream of the Huangshan Mountain

Breeding strategies of Acrossocheilus fasciatus were studied from 592 specimens collected monthly during May 2007 and April 2008 in the Puxi Stream of the Huangshan Mountain. Sex ratio of the studied population was 0.90 ： 1 （ ♀ ： ♂ ）, not significantly different from 1 ： 1. Both sexes reached their first sexual maturity at age 2 （the second calendar year of their birth）. Fifty percent of females and males reached maturity at a total length of 69.75 mm and 69.36 mm respectively, and the minimum total length was 61.54 mm and 58.96 mm, respectively. Based on the monthly changes in gonado-somatic index and egg- development process, the breeding season of the population was from May to August, with one obvious interval （in June） occurring in the breeding activity for the females. The nonsynchronous development of oocytes observed in mature ovaries indicated that A. fasciatus is a batch spawner. Absolute fecundity of A. fasciatus ranged from 308 to 2002 eggs with a mean of 857 eggs, increased significantly with total length, and was significantly different among three age groups. Relative fecundity ranged from 38.63 to 71.70 egg/g with a mean of 53.29 egg/g, and was not significantly different among the three age groups. It was suggested that these reproductive characteristics were adaptive strategies for A. fasciatus to acclimatize to lotic water where environmental factors were unstable but predictable [ Current Zoology 55 （5） ： 350 - 356, 2009].

Reproductive biology of Schizopygopsis younghusbandi Regan 1905(Cyprinidae:Schizothoracinae)in the middle reaches of Yarlung Tsangpo River,China

The reproductive biology of Schizopygopsis younghusbandi(Cyprinidae: Schizothoracinae) was studied by 719 individuals that collected from August 2008 to August 2009 in the middle reaches of Yarlung Tsangpo River, China. We coupled monthly variations of the gonadosomatic index(GSI), monthly proportions of the macroscopic maturity stages with size distribution of oocytes to evaluate spawning seasons. Taken as a set, these results indicated that S. younghusband i spawned from March to April with high degree of the spawning synchronicity. The standard lengths and the ages at 50% maturity for male were 222 mm and 4.4 year, and 308 mm and 7.0 year for female. In addition, the estimated mean fecundity and mean relative fecundity were 18682 and 57.8 eggs per g body weight. The fecundity of S. younghusbandi increased linearly with increasing of standard length and body weight. This study provides details about the S. younghusbandi reproduction suggesting that may be this species is vulnerable to exploitation in the middle reaches of Yarlung Tsangpo River.

Gonadal maturation and histological observations of the grey triggerfish Balistes capriscus Gmelin,1789(Teleostei:Balistidae)in the Gulf of Gabès,Tunisia

Objective:To determine the spawning activity using gonadosomatic index(GSI)and gonad histology the Balistes capriscus(Teleostei:Balistidae)of the Gulf of Gabès(Southern Tunisia,Central Mediterranean Sea).Methods:The reproductive biology of the species,based on 756(480 females and 276 males),collected from commercial catches at several fishing ports including Chebba,Kerkennah and Zarzis at respective GPS coordinates(34°14'N,11°06'E),(34°45'N,11°17'E),(33°41'N,11°48'E)was studied over 28 months(January 2008-April 2010)using GSI and gonad histology.Sizes used in this study ranged from 11.30 to 45.60 cm in fork length.Results:Both GSI and gonad histology suggest that spawning activity occurred mainly between July and mid-September with a peak in July,coinciding with summer time.The first maturation occurred at 20.26 cm fork length for females and 21.30 cm fork length for males.The monthly values of hepatosomatic index and condition factor(K)indicated that the liver is the main organ responsible for the mobilization process of the energizing reserves during the sexual cycle.Conclusions:It is the first inventory of gonadal maturation and histological observations of the grey triggerfish Balistes capriscus Gmelin,1789(Teleostei:Balistidae)in the Gulf of Gabès,(Southern Tunisia,Central Mediterranean Sea).