Size at maturity of splendid alfonsino (Beryx splendens) from the Emperor seamounts
Analysis of splendid alfonsino data collected by NPFC members for the purpose of determining spawning season, maturity stages, and size at maturity for stock fish around the Emperor seamounts. To mitigate sampling bias and maturity stage inconsistencies in the existing data set, we calculated maturity using the gonadosomatic index (GSI) of female alfonsino using the gonometric method described in Flores et al (2019). Based on this test, we found a GSIcut-off score of 0.51 and k coefficient of 0.67 for Japanese data, however, both Korean and Russian data was not applicable for this analysis. Based on our gonometric results, FL50 was 282.1 mm among fish sampled by fishery trawl and 265.5 mm for fish sampled by fishery gillnet. Further analyses on size and maturity revealed that the difference between gears is likely to be a result of different gear selectivity, and that different seamounts host alfonsino with different size and size at maturity. While we believe the gonometric method can potentially function as an accurate yet cheap way to determine stock maturity, it is currently in the preliminary phase of testing and so we cannot recommend it for use in stock management.