Nancy Lo

Molecular identification of Ammodytes (PISCES, Ammodytidae) larvae, with ontogenetic evidence on separating populations

A total of ten larval Ammodytes were collected from the Yellow (5 specimens) and Bering Seas (5), and a 638 base pair sequence from their mitochondrial DNA COI genes was analyzed for species identification. Sequences were compared with those of adult Ammodytes personatus from the East (4), the Yellow (2) and the East China Seas (2), and Japan (3). Average genetic distance was 0.064 between the Yellow Sea larvae and the Bering Sea larvae, but was 0.0043 between the Yellow Sea larvae and all the adult A. personatus except two individuals from the East Sea. NJ-tree showed that five Yellow Sea larvae were closely clustered with adult A. personatus, except for two individuals. The five Bering Sea larvae were located distantly from adult A. personatus, and are thought to be A. hexapterus. We found morphological differences among two populations of A. personatus larvae and A. hexapterus larvae in morphometric characters and pigmentation. Our results indicated that the East Sea population of A. personatus is closer to A. hexapterus than to the Yellow Sea population of A. personatus, suggesting the East Sea population may be part of separate species.

Application of a stage-specific matrix model and length-cohort based analysis to assess the anchovy fishery in Catalan coastal waters (NW Mediterranean Sea)

Abstract This study describes trends in anchovy ( Engraulis encrasicolus ) population biomass in Catalan coastal waters of the northwestern Mediterranean Sea and relates empirical data to the demographic models in order to understand its dynamics and shed some light for future management of the stock. Classical fisheries models (length-cohort analysis and yield-per-recruit analysis) are applied together with the stage-specific Lefkovitch matrix model to detect population growth. Estimates of rates of growth, mortality, and fecundity were assembled for each biological stage. The results confirm and quantify the importance of early life stages on population trends and indicate how sensitive the overall biomass is to rate variations. Both approaches are consistent in indicating stable biomass conditions at the current exploitation level, even though environmental variability is not considered, and might cause changes. In view of the fishermens effort reduction, a 10% fishing mortality decrease on the fishery was also examined in a dynamic model to forecast the yields, simulating different stock-recruitment patterns.