Semi-separable untuned VPA for red drum.

Untuned backwards VPA’s were applied to catch at age data for the northern and southern regions red drum stocks to provide comparisons with estimates of historic stock size from statistical catch at age (SCCA) assessment models. The final year (2007) abundance of age two fish was determined by specifying their fishing mortality (F), and 2007 abundances at other ages were selected with a combination of constraints on selectivity in 2007 and approximate separability of F during 2003-2007. The constraints on selectivity were similar to those used in the SCCA assessment model, and were consistent with tagging information. Age compositions for the release mortality component of the recreational fishery (i.e. B2 catches) were inferred from the harvested age compositions (i.e. A+B1 catches) and the selectivity of the B2 fishery component relative to the A+B1 component, as inferred from a tagging model. The results show that average F for ages 1-3 in the northern region was about 1.5 during 1982-1990 but declined during 1991-1994 and was relatively stable during 1995-2002 with a mean of 0.9. Total abundance during 1982-1997 fluctuated between 200 000 and 400 000, but increased to 660 000 in 1998 and then declined to 160 000 in 2003, th