Optimal harvesting in an age-class model with age-specific mortalities: An example from Namibian linefishing

Namibia’s main linefish species, the kob, is subject to age-specific fishing mortalities that differ for the two fisheries (commercial linefishing vessels and recreational anglers) exploiting it.

The study finds that the planning horizon is crucial when determining the most profitable allocation of kob resources between the two fisheries. With a short planning period, it is optimal to allocate much of the catch to commercial fishing. However, if a longer planning period is used, it is preferable to close down commercial linefishing completely. This is because decreased commercial fishing would increase the availability of the older kob preferred by recreational anglers.