The vertical distribution of eggs and larvae of Maurolicus japonicus were described based on discrete depth oblique tows of a larva net seasonally collected during both day-and nighttimes at a 130 m-depth station near the continental shelf of Tosa Bay. The abundance and diel differences in the vertical distribution of eggs and larvae in relation to physical properties of the water column were also examined. Both eggs and larvae occurred only in spring and neither occurred in other seasons. In spring, water temperature, salinity and specific gravity were less stratified in the water column with a modest upwelling to ca. 100 m-depth, around which the seasonal temperature hardly changed. Unlike the Japan Sea, with a year-round reproduction of M. japonicus, the limited occurrence of eggs and larvae in Tosa Bay was likely related to upwelling in April. Eggs were twice as abundant at night-than daytime, suggesting that this species spawns at night. Most of the eggs were in A and B-stages and aggregated at 30-70 m depth during both the day and night. Larvae that were mainly in preflexion without yolk and flexion stages, were found in the 110-70 m and 130-90 m depth layers during day-and nighttimes, respectively. Earlier larval stages were dispersed abundantly from 130-m to the surface during daytime, with little correspondence to light attenuation or chlorophyll-a concentrations. Compared to the Japan Sea, Tosa Bay yielded various mesopelagic fish species that inhabit and breed in the mesopelagic zone, so that the reproductive niche would be temporally and spatially limited for M. japonicus.
There is paucity of studies relating to fish corral fishery and its management particularly those operated on reef flats. This study was conducted to evaluate the fish catch composition of fish corrals situated in the reef flat of Palompon, Leyte from July 2009 to January 2010. During the monitoring, two sets of data were utilized: the semimonthly field intercept samplings and the daily fish landing data. Field intercept samplings enabled the researchers to approach fishers as they were gathering their fish catch that was eventually identified, sorted, measured, and weighed. Fish landing data recorded by local enumerators included the fish’s local name and corresponding weight. From 27 fish corrals, the intercept samplings yielded a total catch of 23.9 kg, which was composed of 81 identified species under 47 genera from 31 families. The most abundant family was Siganidae comprising 44% of the total catch, followed by Apogonidae (18%) and Pomacentridae (9%). This composition was corroborated by the fish landed data. The temporal and spatial trends of the catch composition showed that Fam. Siganidae was most abundant in the months of July, October, and December, while Apogonidae in the months of August and November. It was observed that there was an unequal spatial distribution of fish species in the study area. Of the four sampling areas, Area 2 on the northeastern part of Palompon was the most diverse due partly to the high number of fish corral units and the area’s structural complexity wherein seagrass and algal beds were most extensive interspersed with coral patches. Results of this study could serve as reference for future studies dealing with monitoring and managing fish corral fishery.
Summary The siganid production in the Philippines is continuously declining from 2007 up to present. In Palompon, Leyte, annual yield of siganids, particularly Siganus canaliculatus (Park, 1797) also showed a decreasing trend of total production. This is consistent that this stock is under heavy pressure, and when left unmanaged, this could lead to further overexploitation and the collapse of the stock in the long run. Regardless of this, detailed reproductive biology and potential of this species are very few in the Philippines. Therefore, this study was conducted to provide information on the reproductive biology and breeding cycle of S. canaliculatus in Palompon, Leyte where fishing pressure is high and sound management formulation is necessary. S. canaliculatus is a group‐synchronous, multiple spawners with skewed sex ratio where males predominates over females. Maturity stages based on macroscopic examinations identified four maturity stages (immature, developing, mature and spent) while six maturity stages (immature, developing, mature, spawning, spent and re‐developing) were identified through histological analysis. A single ovo‐testis was identified among the 669 specimens examined. Based on histological sections, the smallest size of mature male was 5.5 cm standard length, and the smallest mature female was 7.1 cm standard length. On the other hand, length at first maturity for mature fish were 8.1 cm standard length for males and 9.7 cm standard length for females. Two defined peaks of gonadosomatic index were identified in both sexes: a major peak from February to May and a minor protracted one from July to December. Mature and older ovaries and testes occurred throughout the year, an indication of your round breeding season of S. canaliculatus in Palompon. Implementing a fishing ban during the major and the minor breeding spawning peaks would allow the mature and older individuals to contribute first to the population; allowing the continuity of the stock.
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