Preliminary trial on laboratory-induced spawning of lokan Polymesoda erosa (SOLANDER 1786)

Lee, Kar Fei (2009) Preliminary trial on laboratory-induced spawning of lokan Polymesoda erosa (SOLANDER 1786). Universiti Malaysia Sabah. (Unpublished)


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This research was conducted to determine the size and rate of exploitation, to determine size of maturity; and possibility of laboratory-induced spawning of lokan (Polymesoda erosa). The study site is nearby Salut Bay in Kota Kinabalu (060 06'05.5" N, 1160 09'58.5" E). Sampling was conducted from June-October 2008. Baseline information about the resource was obtained primarily through interview with the locals, and actual participation at the collecting sites. Lokans were collected every week during study period, with a frequency of two to three times per week. The timing of the collecting coincided with tidal and lunar period, and the frequency of collecting might increase with market demand. Each collecting trip between three to four hours, with a catch per unit effort (CPUE) of 400 to 1000 individuals of lokans; in general, very small size «1 cm shell width) lokans are not collected. Based on histological observations, the size of maturity of the lokan was determined to be approximately 42 mm shell width. The two induced spawning trials gave negative results, although all the brood stock survived the conditioning period (34 and 35 days, respectively) except two were dead from Trial 2. A further histological observation was conducted to determine the maturity stage of the bloodstocks; The results based on six specimens (40 to 49 mm) from Trial 1; and four specimens (50 to 59 mm) from Trial 2 showed that all, except two specimens were in the ripe phase. Of the two (which were not in the ripe phase), one showed late active phase (Specimen 3, 41.8 mm), whilst the other showed partially-spawned phase (Specimen 6, 53;9 mm); This indicates that although brood stock conditioning treatment was successful, however, they retained their gametes due to their natural synchronized spawning behavior. Findings of this study provide a clear picture how lokan are being harvested and also the exploitation rate of the resource. Results of the induced spawning trials serve as basic information for future studies.

Item Type: Academic Exercise
Uncontrolled Keywords: lokan (Polymesoda erosa), size of maturity, rate of exploitation, market demand, tidal and lunar period, broodstock, spawning trial
Subjects: Q Science > QL Zoology
Divisions: SCHOOL > School of Science and Technology
Date Deposited: 09 Jul 2013 03:59
Last Modified: 23 Oct 2017 06:33

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