Reproductive Biology of Terapon Jarbua from the Estuary of Tamshui River

The larval anchovy fishery is one of the most important coastal fisheriesin Taiwan.The species caught mainly belong to the Family Engraulidae.Inthis paper,the factual distribution conditions of larval anchovy from thecoastal waters of Fang-Liao by means of hydroacoustic survey was studied.Serial observations on temperature and salinity were simultaneously recorded.The results are as follow:(1)The species caught was mainly composed of Engraulis japonica andpartly Stolephorus zollingeri and Stolephorus heterolobus.The optimal ranges oftemperature and salinity for Stolephorus were wider than those for Engraulisjaponica,while the optimal osmotic pressure ranges of the above two generawere 25.75-25.9 and 25.58-25.76atm,respectively.(2)Several larval anchovy schools may form a unique fish shoal alongtheir optimal osmotic pressure regions.The margin of fish shoal wasbordered by the flow axis of river discharge with low osmotic pressure andthat of offshore current with high osmotic pressure.(3)The composition of daily catch fluctuated with sea surface temperature(SST)and so did the composition of annual catch.When the southernoscillation index was strongly negative(i.e.E1-Nino)and the SST in winterwas anomalously warm,the major composition of caught species belonged toStolephorus.On the other hand,when the environmental condition wasresversal,the main catch became Engraulis japonica.