Download
1 / 5
50 likes | 112 Vues
Request 1: Compare growth differences between Arora (1951) and Lefebvre (2012) or simply compare mean length-at-age. Rationale: To determine whether fishing caused life history changes were also observed in estimated growth and maturity. .
E N D
Request 1: Compare growth differences between Arora (1951) and Lefebvre (2012) or simply compare mean length-at-age. Rationale: To determine whether fishing caused life history changes were also observed in estimated growth and maturity.
Response: The Arora fish were aged primarily by scale annuli and scale widths, although otoliths were somehow included in the criteria (actual aging method not entirely clear). Thus, the mean size at age data may not be directly comparable. However, there is no evidence of a dramatic difference between mean size at age from Arora (n=87) and that from the aged fish from the trawl survey (n=~7000)
Historical catches (16 to 30 from FB 74, aggregatred spp, 31-68 from reconstruction). The flatfish fishery was very well developed by 1915- with total catches mostly of shallower water flatfish- English sole, California Halibut, Pacific sanddab, Starry Flounder and various turbots. As Petrale, Dover sole, other deeper spp. Were targeted, the % of flatfish catch that was sanddab declined.Note too that even while the fishery was well developed, Pac dabs were never a huge component, partially consistent with there not being a huge volume of available biomass.
Relative to potential significance of other sanddab species: Of 11,551 Sanddabs identified to species level in California port samples since 2003 (when more attention paid to sanddabs), 11,308 (~98%) were Pacific sanddab. Of 2466 Sanddabs identified in the 2001-2005 Groundfish Ecology Study (in Monterey Bay), 2454 (99.5%) were Pacific sanddab.
Exploitation rates (catch/total biomass) for base Sanddab model relative to English sole and Starry flounder (latter assumes the equil. Starting biomass level- that model started in 1970). Note that catches in early 1900s were focused on central CA where relative exploitation rates would have been much greater – point is simply that Sanddab exploitation rates were comparable to those of other shallow water flatfish..
