The South Coast Rock Lobster resource (Palinurus gilchristi)
The fishery: This is a capital intensive commercial fishery dating to
1973 with annual landings of about 400 tons tail weight worth US$ 15 million.
The typical fishing depth is 100 fathoms and the fishery is situated along the
South African South Coast. There were 9 vessels operating in 2002, six of whom
are represented by the South Coast Rock Lobster Association. The fishery is
managed by a total allowable catch (TAC), individual quotas and a closed season.
Product types include live, frozen tails, whole cooked and whole raw frozen.
Brief review of management issues and OLRAC's involvement:
OLRAC has been involved in the scientific management of this resource since
1991. Scientific input by OLRAC has been facilitated by Drs Bergh and Barkai's
presence at the Rock Lobster Working Group, a scientific committee within the
government research agency, the Sea Fisheries Research Institute (SFRI). The
fishery has been challenged by a number of conservative management proposals,
driven in 1991 by the perception that the fishery was in decline. Although this
perception was logically linked to an observed decline in catch rate, closer
analysis showed that the negative catch rate trend was an artifact of a change
in effort regulations, which led to effort underreporting on official return
forms during the early period of the fishery. When the correct effort data were
collected, the new catch rate trend did not show the previous large decline.
For a while, a status quo TAC was adopted. OLRAC continued to carry
out research on behalf of the association, focusing on catch rate and mean size
trends, and the spatial pattern of the deployment of fishing effort.
New scientific arguments were developed in 1993 and 1994, based on a General
Linear Modeling (GLM) analysis of the commercial catch rate database concerned
mainly with the possibility of increases in fleet efficiency, and a Bayesian
surplus production model analysis of the year to year trends in resource
abundance. OLRAC's research showed that a more statistically acceptable version
of the GLM which addresses individual vessel efficiency factors should be used.
OLRAC also showed that a statistical analysis of tagging results places an upper
bound on the harvest proportion and a lower bound on recent resource biomass
levels. Following a heated debate, the TAC was reduced only gradually, first by
25 tons per annum, and more recently by 12.5 tons per annum. However,
independent mathematical and statistical results have been produced by OLRAC,
which suggest that the present framework within which the resource is now being
managed may be ill-founded. These analyses include:
- A size based Bayesian assessment procedure for the resource, using commercial pack category information for different sizes of lobsters,
- Updates of the tagging data analyses, showing that the harvest proportion is still less than 15%, and
- An analysis which shows that the reduction in catch rate in the fishery is most probably the result of an escalation in effort due to intense competition between skippers for their share of each company's individual quota, rather than a reduction in resource biomass.
