魁蚶稚贝的底质选择性及其潜沙能力评价

Substrate preference and burrowing ability assessment of the juvenile Scapharca broughtonii

底质是魁蚶稚贝潜沙、水平移动、存活与生长的重要环境因素,选择底质适宜的海区开展底播增殖,可以有效提高魁蚶稚贝的增殖效果,但目前仍缺乏相关研究。因此,在实验室条件下,研究了10 mm<壳长<15 mm、15 mm<壳长<20 mm、20 mm<壳长<25 mm、25 mm<壳长<30 mm 4种规格魁蚶稚贝对4种底质粒径(细砾、粗砂、中砂、细砂)的选择模式,并量化分析了20 mm<壳长<30 mm稚贝在5种底质粒径(增设泥底质)条件下的潜沙能力。结果表明:(1)10 mm<壳长<15 mm稚贝的足丝较发达,以附着生活为主,明显偏好粗砂底质,其在两种底质交界位置的分布率、水槽的贴壁率均最高;15 mm<壳长<30 mm稚贝转入营埋栖生活,随着规格的增大,稚贝选择的底质粒径亦增大,而在2种底质交界位置的分布率、水槽贴壁率也随之减小。其中15 mm<壳长<20 mm稚贝偏好选择中砂,分布率为50.50%,其次为细砂;20 mm<壳长<25 mm稚贝对不同粒径底质的适应性均较强;25 mm<壳长<30 mm稚贝偏好选择粗砂底质,分布率达到65%,其次为中砂。(2)20 mm<壳长<30 mm稚贝在淤泥底质中的初潜时间最短,为2.74 min,其次为中沙、细沙;在细砂底质中的潜沙率最高,达到85%,其次为中沙。综合分析认为,20 mm<壳长<30 mm稚贝是较适宜的底播苗种规格,而以中砂(0.25 mm<粒径<0.5 mm)和细砂(粒径<0.25 mm)为主要粒径组成的海区宜进行魁蚶稚贝的底播增殖。

Behavioral preferences of juvenile Scapharca broughtonii with 10 mm 〈 shell length 〈 15 mm, 15 mm 〈 shell length 〈20 mm,20 mm 〈 shell length 〈 25 mm,25 mm 〈 shell length 〈 30 mm to four kinds of substrates （granule gravel, coarse sand, medium sand, and fine sand）were studied under laboratory, conditions and then the burrowing ability of 20 mm 〈 shell length 〈 30 mm juvenile S. broughtonii to five kinds of substrates （ mud group added） was investigated. The results showed that 10 mm 〈 shell length 〈 15 mm juveniles have a developed byssi and mostly in sessile life with the highest distribution rate at the junction between substrates and percentage of hanging on the tank walls. Also, these were significantly attached on coarse sand. The 15 mm 〈 shell length 〈 30 mm juveniles changed into infaunal life and grain sizes preferred by them increased with the increase of shell length,accompanying a decrease in the percentage of laying in junction and percentage of hanging on the tank walls. The 10 mm 〈 shell length 〈 20 mm juveniles preferred medium sand significantly with a distribution rate of 50.5 % , then the fine sand. The 20 mm〈 shell length 〈 25 mm had high adaptation to all kinds of substrates. The 25 mm 〈 shell length 〈 30 mm juveniles preferred coarse sand significantly with a distribution rate of 65 % , then the medium sand. The 20 mm 〈 shell length 〈 30 mm juveniles had the shortest burrowing time（2.74 min） at mud, then the fine sand and medium sand. The highest percent of burrowing rate （85%） were attained in the fine sand, then in the medium sand. Our data indicated that 20 mm 〈 shell length 〈 30 mm juveniles and sea bottom mainly with medium （0.25 〈 grain size 〈0.50 mm）and fine sand（ size 〈0.25 mm）are fit for stock enhancement.