Acoustical Estimation of Herring Stock in the Gulf of Riga: An Encouraging Case of Method Implementation In Semi-enclosed Basin

摘要

Although the methodology of acoustic surveys has shown considerable improvements over the recent years, the results of acoustic surveys are not always in good agreement with the results of catch-based analytical assessments. Acoustic research of herring in the Gulf of Riga started in the Latvian zone already in the 1980s. In order to obtain catch-independent tuning data for the assessments and identify the peculiarities of distribution of the Gulf herring the joint Estonian-Latvian acoustic surveys were initiated in the whole Gulf of Riga in 1999. The results show that the Gulf of Riga as a semi-enclosed basin with favourable bottom topography and settled character of gulf herring stock has offered favourable conditions for successful implementation of the results of acoustical surveys into the assessment of gulf herring stock. Acoustically estimated number and biomass of gulf herring in the Gulf of Riga have been in very good agreement with VPA estimates. This allows assuming high reliability of the abundance estimates and geographical distribution pattern of gulf herring stock described in our study.