饲养空间大小对单体筐养养殖系统中三疣梭子蟹(Portunus trituberculatus)的摄食行为与生长特性的影响研究

EFFECT OF SPACE SIZE ON FEEDING BEHAVIOR AND GROWTH OF SWIMMING CRAB PORTUNUS TRITUBERCULATUS IN SINGLECRAB BASKET-CULTURE(SCBC) SYSTEM

在三疣梭子蟹(Portunus trituberculatus)的单体筐养养殖(SCBC)系统中,研究了不同的饲养空间大小对梭子蟹(幼蟹与成蟹)摄食行为与生长的影响。试验设置了四个饲养空间处理:空间长度分别为养殖蟹平均壳长的1倍、1.5倍、2倍及3倍,宽为长的一半。经6天试验,结果表明,1倍空间的幼蟹摄食行为发生变化,摄食次数[(1.2±0.45)次/d]和总进食时间[(31.2±6.89)min]比2倍与3倍的空间[(2.6±0.45)次/d,(83.1±13.66)min]明显减少,导致摄食量减少[前者为(0.0835±0.0269)g/g BW,后两者最高为(0.2014±0.0114)g/g BW],至第5天全部死亡。其它处理,随着空间的增大,摄食量增大,幼蟹的生长速率(蜕皮率,体重增长率)增加。其中,在2倍空间以上处理中,幼蟹表现有最高的成活率(100%)、蜕皮率(100%)以及体重增长率(86.5%—97.2%),同时有较低的饵料系数(1.31±0.11)。成蟹的试验结果与幼蟹类似,除1.5倍饲养空间外,该处理中幼蟹表现出对生长的胁迫,而成蟹的摄食行为和生长与2倍及3倍空间无差异。不同空间中梭子蟹的摄食与生长的差异与梭子蟹在这些处理中的保护性酶类(SOD,POD,CAT)和消化酶类(淀粉酶,蛋白酶,脂酶)的活性有密切关系。

To understand the impact of individual size of a single-crab basket-culture(SCBC) system on feeding behavior and growth of swimming crab Portunus trituberculatus, four sizes were designed in a 6-day experiment with polyethylene boxes in dimensions of, i.e., 1, 1.5, 2, 3 times of the average carapace length of tested animal as the length, and the half size as the width. The crabs for experiment included two sizes in average weight of(0.89±0.14)g(juvenile) and(57.68±6.09)g(adult) and acclimated in salinity of(20±0.5) at(26±1)°C in sandy bottom for 4 days. Feeding was provided at 9:00 am daily, and the animal ate the feed for 25—30 minutes in 70 min. Water was refreshed daily before feeding. Results show that the size groups of 2 and 3-times of carapace length showed a slight difference in feeding behavior from that of 1 time-length group. The crabs from different treatments had different molting rates and mortality rates. All juveniles in 2 and 3 time-length sizes molted during the experiment, which was significantly higher than that in other treatments. The mortality rate showed the opposite pattern as that of the molting rate, all juveniles were alive in 2 and 3 time-length groups. The adult crabs showed similar results with the juvenile except in 1.5 time-length group, which had no difference from that of 2 and 3 time-length groups. The juveniles had the highest value of food ration for(0.2014±0.0114)g/g BW, average body weight gain of(0.812±0.135)g, gain rate of 86.5%—97.2%, and food conversion ratio for(1.31±0.11) in 2 and 3 time-length groups; in addition, the treatment also had the lowest activities of protective enzymes(SOD, PO, CAT) and the highest activities of digestive enzymes(amylase, protease, lipase). Therefore, the size dimension affected the activities of protective and digestive enzymes, causing the difference that mentioned above.