A spatial- and age-structured assessment model to estimate the impact of illegal fishing and ecosystem change on the South African abalone Haliotis midae resource

The management of abalone stocks worldwide is complicated by factors such as illegal fishing combined with the difficulties of assessing a sedentary (but not immobile) resource that is often patchily distributed. The South African abalone Haliotis midae fishery is faced with an additional problem in the form of a relatively recent movement of rock lobsters Jasus lalandii into much of the range of the abalone. The lobsters have heavily reduced sea urchin Parechinus angulosus populations, thereby indirectly negatively impacting juvenile abalone which rely on the urchins for shelter. A model is developed for abalone that is an extension of more standard age-structured assessment models because it explicitly takes spatial effects into account, incorporates the ecosystem change effect described above and estimates the magnitude of substantial illegal (‘poached’) catches. The model is simultaneously fitted to catch per unit effort and Fishery-Independent Abalone Survey abundance data, as well as to several years of catch-at-age (cohort-sliced from catch-at-size) data for the  various components of the fishery and different spatial strata. It constitutes the first quantitative approach applied to the management of this commercially valuable resource in South Africa and has provided a basis for management advice over recent years by projecting abundance trends under alternative future catch levels. Keywords: abalone, ecosystem change, fisheries management, Haliotis midae, illegal catches, poaching, spatial modelling, stock assessment, TURFAfrican Journal of Marine Science 2010, 32(2): 207–23

Assessment of the South African hake resource taking its two-species nature into account

The commercially valuable hake fishery off South Africa consists of two morphologically similar species, the shallow-water Cape hake Merluccius capensis and the deep-water Cape hake M. paradoxus. Because catch-andeffort statistics collected from the fishery are not species-disaggregated, previous published quantitative assessment methods have treated the two hake species as one. Furthermore, recent evidence suggests that (although treated as two separate populations in past assessments) the South and West coasts components of each species form a single stock. This paper describes the development of the first fully species-disaggregated coast-wide baseline assessment of the South African hake resource. M. paradoxus is estimated to be currently a

A history of recent bases for management and the development of a species-combined Operational Management Procedure for the South African hake resource

The bases for historical catch limits placed on the hake fishery are reviewed in brief for earlier years and then in some depth over the period from 1991 when the Operational Management Procedure (OMP) approach was introduced for this fishery. The new OMP implemented from 2007 was the first to be based on the use of rigorous species-disaggregated assessments of the resource as Operating Models. The paper describes the Reference Set and range of robustness trials, together with the associated Operating Models, which were used for the simulation testing of the new OMP. Performance statistics for a number of candidate OMPs are compared, and the two key trade-off decisions in the selection process discussed (substantial Merluccius paradoxus and catch per unit effort [CPUE] recovery, and total allowable catch [TAC] stability constraints). Details of the OMP adopted and how its formulae depend on recent trends in CPUE and survey estimates of abundance are provided. OMP-2007, which is tuned to a median 20-year recovery target of 20% of pristine spawning biomass for M. paradoxus and a 50% increase in CPUE over the next 10 years, has been adopted for recommending hake TACs over the 2007–2010 period until the next scheduled major review. A set of general guidelines adopted for the process of possible overruling of recommendations from OMPs or bringing forward their reviews within an otherwise intended four-year cycle is detailed. Keywords: hake; Merluccius; management; management procedure; OMP; South AfricaAfrican Journal of Marine Science 2008, 30(2): 291–31

Lobster aquaculture development in Vietnam and Indonesia

Development of spiny (rock) lobster aquaculture is of special interest because market demand continues to increase while capture fisheries production remains static and with little likelihood of any increase. This chapter provides a synopsis of information about the history, development, status and future of tropical spiny lobster aquaculture with a particular focus on Vietnam and Indonesia, where considerable development has already occurred. Vietnam is the only country in the world where farming of lobsters is fully developed and commercially successful. The Vietnamese industry is based on a natural supply of seed lobsters – the puerulus stage, as hatchery supply is not yet available due to the difficult technical demands of rearing spiny lobster larvae in captivity. Vietnam currently produces around 1,600 tonnes of premium grade lobsters, primarily of the species Panulirus ornatus, that are exported to China where price is greatest. The industry is valued at over $US120 million. That success led to significant interest in Indonesia where a fishery for seed lobsters has become well developed, with a catch 10 to 20 times greater than that of Vietnam. However, growout of lobster in Indonesia remains insignificant due to adverse government policy and lack of farmer knowledge and skills. The seed lobsters available in Indonesia are primarily Panulirus homarus, a species with excellent production characteristics like P. ornatus, although with lesser value. Extraordinarily high abundance of naturally settling seed lobsters is apparent in selected areas due to a confluence of suitable conditions that create a high concentration of late stage larvae near the coast. These areas have been termed hotspots, as the availability of settling seed is much higher than other areas. Such hotspots are now recognized for the central northern coast of Vietnam – supplying their growout industry and the central southern coast of Indonesia. Natural mortality of the seed lobsters in these areas is correspondingly high due to insufficient settlement habitat and fish predation. Consequently, responsible fishing of these seed is sustainable, providing a valuable resource that can be on-grown for benefit of impoverished coastal communities. Innovative and inexpensive techniques have been developed to effectively catch the seed as they swim towards the coast seeking suitable habitat. In Vietnam, the seed are typically sold by fishers to dealers, who aggregate supplies and then on-sell to nursery farmers. Nursing consists of rearing the seed lobsters in small suspended or submerged cages, with a diet of fresh seafood – crabs, mollusc and fish. Advanced juvenile lobsters are produced that are in turn on-sold to growout farmers who stock them to larger floating cages, suspended from simple floating frames. The economics involve relatively low capital and operating costs, and production of high value product, that provides significant economic and social benefit to the communities involved. Although several health and disease issues have impacted spiny lobster farming, they can be effectively managed through good nutrition and husbandry. Market demand for spiny lobster from China is strong and growing, far exceeding supply. There appears to be great scope for much larger farm production of spiny lobsters with little impact on price. The future for tropical spiny lobster aquaculture appears to be very positive, particularly for developing countries in the Asian region, where seed are available, suitable growout locations are present and where costs of production are relatively low. It is expected that lobster aquaculture will continue to develop in the region, expanding beyond Vietnam and Indonesia