2019 STAR Panel: Length-based selectivity

[chantelwetzel-noaa]

Consider (and potentially adopt) length based selectivity for the WCGBTS, as selectivity bias could lead to observed age zero fish not being a good representation of mean length at age 0 (which could affect estimates of growth). Figure 13 (below) shows some summary results of this issue, including the lack of apparent growth of age 0 sablefish during the period of the survey. A related issue is that specifying the size at age 0.5 (or 1.5), as well as the CV, should be in common by sex. Dimorphic growth presumably occurs at older ages. Future assessments should consider configuring “offsets” for sex differences in the growth. The rationale for this change is that differences between sexes at such young ages seem unlikely and re-configuring the model in this way will reduce the number of parameters needed.

To Do:

• Explore offsets in growth which would allow male and female growth CV at young ages to be the same. This would depend upon whether issue 2019 STAR Panel: Weight-at-age #3 was implemented.
• Explore how to estimate selectivity for sablefish depending upon how growth is modeled.