Studies On Biological Characteristics Of Monodanta Labio And Omphalius Rusticus In Coastal Area Of Zhoushan

This study is mainly concerned with Monodanta labio and Omphalius rusticus fromZhoushan.4290samples were collected from January2012to January2013(3662samplesof M. labio,628samples of O.rusticus). Their natural population structure (shell height,gross weight, relative fatness, gender, age), gonad development, feeding and analysis ofquantitative traits were researched respectively.By statistically analyzing the population structure of M. labio, the data demonstratedthat the annual distribution of shell height range from2.96to28.20mm with the mostfrequent range from10.00to15.00mm, while the young less than5.00mm in shell heightbatch appeared in October. Most of them belong to the group2~+, all aging from0~+to5~+.The majority of samples weighing from0.0158to7.1280g were considered to1.0~1.5gweight. There has been no obvious regularity about changes from month to month in shellheight、age and gross weight. The range of relative fatness was19.12%to41.99%andpeaked in June(39.83%). The results showed that the stage of Gonad maturity andspawning were mainly concentrated in May to October. No gonad development can befound in snails that have less than5.0mm height, However, most of the samples shellheight ranging from10.0to15.0mm had gonad development with the male and femaleratio was1.04:1. In addition, all the snails ranging from15.0to20.0mm in shell heightsalmost developed, and the ratio was1.67:1. The rate of males and females fit the regularpattern first up and then down along with the increasing of shell height.The results of relative analysis about O.rusticus demonstrated that annual distributionof shell height ranges from4.72to28.00mm with the most frequent range from10.00to15.00mm, while few less than5.00mm height or more than25.00mm height had beenfounded. Most of them belong to the group2~+, all aging from0~+to5~+. The majority ofsamples weighing from0.1856to11.2322g were considered to2.0~3.0g weight. There hasbeen no obvious regularity about changes from month to month on shell height, age andgross weight. The range of relative fatness was16.41%to34.15%and peaked inJuly(33.27%). The results showed that the stage of spawning were mainly concentrated in July to October. No gonad development can be found in less than5.0mm height. However,most of the samples from10.0to15.0mm height had gonad development with the maleand female ratio was1.10:1. In addition, all the snails having the height ranging from15.0to20.0mm almost developed, and the ratio was1.21:1. Only four had been collected over25.00mm height, and all are male. The rate of males and females fit the regular pattern firstup and then down along with the increasing of shell height, which is also the case in M.labio.By the anatomy of stomach and radula of above two snails and analyzing relative data,Despite a little single-celled diatoms, the food structure consisted of many organic detritus.Further, correlation analysis, curve estimation and stepwise multiple regression analysisare used based on weight traits and phenotypic traits of M. labio and O. rusticus in thispaper. All the data distributed to separately establish the multiple regression equation offour phenotypic traits to shell weight and meat weight.According to the regulation about gonad development, breeding and fatness of M.labio, the optimal exploitation period are May and June in theory while forbidden toexploitation from July to September. Compared to the M. labio whose mean height is about30mm with a max height40mm gathered from Pacific northwest, our results demonstratedthat the mean level is about25.00mm of samples separately collected from Fujian provinceand Vietnam(Obtain in the zhoushan market). Therefore, we come to the conclusion that M.labio along the coast of zhoushan has been in serious trend of lowering ages which isassociated with the opening of many ocean areas, excessive exploitation and disorderlycatching. We propose that barred exploitation in some specific islands for several years,and then assess the effects to extend on the purpose of keeping M. labio resourcessustainable and effective use.The optimal exploitation period of O. rusticus are considered June and July andinhibiting catching from August to October according to data in this research owing to therelative few samples.