caa a22 4500 397550707 CHVBK 20180308164749.0 cr unu---uuuuu 161202e199604 xx s 000 0 eng 10.1006/jmsc.1996.0071 doi (NATIONALLICENCE)oxford-10.1006/jmsc.1996.0071 Hampton Ian Sea Fisheries Research Institute, Private Bag X2, Roggebaai, Cape Town 8012, South Africa Acoustic and egg-production estimates of South African anchovy biomass over a decade: comparisons, accuracy, and utility [Elektronische Daten] [Ian Hampton] The spawning biomass of South African anchovy (Engraulis capensis) has been estimated acoustically and by the daily egg-production method every year since 1984. Recruit biomass has been estimated acoustically every year since 1985. The estimates are evaluated, chiefly through comparisons between the acoustic and egg-production estimates. The mean of the acoustic spawner biomass estimates, obtained using a recently developed target-strength expression, agreed to within 10% of the egg-production mean, supporting the expression. The results are consistent with those from a population dynamics model which indicated relatively little bias in the acoustic estimates of spawner biomass compared to the corresponding recruit estimates, which the model indicated to be substantially negatively biased. The coefficient of variation in estimates of spawner biomass, obtained by scaling the current acoustic estimate by the average ratio between previous egg production and acoustic estimates, was typically 21%. It is considered that the value of further egg-production estimates in estimating anchovy biomass is diminishing, and that effort should be concentrated on improving the accuracy of direct acoustic estimates. Ways in which the different estimates have been used to manage the fishery over the past 10 years are briefly described and their utility discussed. It is concluded that the survey results have reliably reflected the major changes in anchovy recruit and spawner biomass that have occurred between 1984 and 1994, and have provided valuable information for managing the fishery over this period. © 1996 International Council for the Exploration of the Sea Regular Articles nationallicence acoustics nationallicence anchovy nationallicence egg production nationallicence Engraulis capensis nationallicence ICES Journal of Marine Science Oxford University Press 53/2(1996-04), 493-500 1054-3139 53:2<493 1996 53 icesjms https://doi.org/10.1006/jmsc.1996.0071 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1006/jmsc.1996.0071 text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- Hampton Ian Sea Fisheries Research Institute, Private Bag X2, Roggebaai, Cape Town 8012, South Africa NATIONALLICENCE 773 0- ICES Journal of Marine Science Oxford University Press 53/2(1996-04), 493-500 1054-3139 53:2<493 1996 53 icesjms Metadata rights reserved CC BY-NC-4.0 http://creativecommons.org/licenses/by-nc/4.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-oxford