Ecosystem Approach to the South African small pelagic fishery
The application of the Ecosystem Approach to Marine Resources (EAMR) is a priority for the EUR-OCEANS network. EAMR frameworks are adaptive, incremental and geographically specific. In this Fact Sheet we report on the implementation of the EAMR to the small pelagics fishery off South Africa. The EAMR requires a sound scientific base to provide the means of assessing the ecosystem effects of fishing as well as the effectiveness of the various management strategies adopted in response to identified risks or effects. Ecological Risk Assessment was adopted in South Africa as a means of identifying and prioritising problems associated with selected fisheries in the Benguela region. To illustrate how South Africa is moving toward an EAMR from the basis of biological research, selected ecological issues raised for the purse seine fishery for small pelagics (anchovy Engraulis encrasicolus and sardine Sardinops sagax) are examined. The indicators required to address these issues are identified and the scientific research or monitoring studies necessary to inform these indicators are proposed. Biological or catch data are synthesised into useful indicators that enable changes and ecosystem responses to be followed in a manageable and formal way (e.g. through specific management measures). Technical management measures that may contribute to solving the issues are also suggested. This will contribute to a management strategy that optimizes social and economic benefits without compromising the integrity and sustainability of the resource and its supporting ecosystem.
The small pelagic fishery
South Africa’s fishery for small pelagics developed off the west coast in the late 1940’s and targeted primarily sardine Sardinops sagax. Catches of this species peaked at just over 400 000t in the early 1960’s but declined rapidly thereafter, the collapse of the sardine stock being ascribed to over-fishing, a southward expansion of the fishing grounds, and variable recruitment. To compensate for reduced sardine catches, the fishery switched to smaller-meshed nets in 1964 to target anchovy Engraulis encrasicolus, which replaced sardine as the dominant component of sardine landings. Following an increase in sardine abundance arising from a management strategy that aimed to rebuild the sardine stock, catches of the two species have been at similar levels since the mid-1990s. Round herring Etrumeus whiteheadi is also targeted but to a lesser degree by the fishery.
Almost all of the anchovy and round herring caught are reduced to fishmeal and oil in industrial-scale factories located on the west coast, whereas some sardine are canned or frozen for human consumption or as pet food or used as bait. Most of the anchovy catch is taken inshore off the west and south-west coasts, and is made up mainly of recruits of around 6 months old that are migrating from the west coast nursery grounds to the spawning grounds on the south coast. Catches of sardine have been made off both the west and south coasts, but in recent years the sardine population has shown an eastward shift and catches are now taken almost entirely off the south coast.
It is estimated that the annual value of pelagic landings for the period 2001 - 2004 was approximately €82 million. The industry provides employment to approximately 4 500 full-time personnel, 2 500 seasonal workers and more than 700 fishers. The support service industries support a further 2 400 indirect jobs.
Management of the pelagic fishery is via an operational management procedure that aims to achieve an optimal trade-off between maximising overall catches of sardine and anchovy and minimising risk of resource collapse. Because anchovy and sardine school together as juveniles, directed fishing on anchovy recruits results in a by-catch of juvenile sardine, hence catches of the two species cannot be maximised simultaneously. Separate total allowable catches are set for anchovy and sardine, in addition to a total allowable bycatch set for juvenile sardine taken in anchovy-directed fishing. Additionally, a precautionary upper catch limit is set for round herring.
Applying the Ecosystem Approach to the South African small pelagics fishery
In implementing the EAMR in South Africa a range of indicators, issues, technical management approaches and potential for implementation are identified for each fishery. Each issue is classified and prioritised according to risk levels. The table below provides some examples of how the EAMR is being applied in the South African small pelagic fishery.
|The Issue||Indicators||Research Approaches||Technical Management||Implementation|
|Impacts of removal of forage fish on species bound to breeding sites on land (i.e. seabirds)||Bird population sizes; breeding success (fledgling weight, fledglings raised per breeding pair, breeding proportion); seabird diet composition; spatial indicators(e.g. overlap of seabird foraging and pelagic fisheries)||Routine monitoring of seabird colonies; satellite tracking to assess foraging ranges; minimum realistic models; spatialised models of pelagic fish around seabird colonies
Quantify and formalise the link between the pelagic fishery and seabirds; quantify functional responses of seabirds to small pelagic prey and identify thresholds below which there are serious negative implications for seabirds
|Avoid populations falling below levels that exceed limit reference points according to IUCN conservation criteria by reducing TACs or closing areas within foraging ranges; allow sufficient escapement of forage fish for predators; avoid threshold levels of pelagic fish below which the implications for seabirds are detrimental||Good potential for implementation of management response/ability to manage|
|Poor understanding of decadal scale fluctuations in abundance of small pelagic fish and thus availability to fisheries||Biomass; catches; trophic replacement index; diet of predators (e.g. seabirds)||Develop indicators to track ecosystem changes; hindcast to pre-fishing period to provide information on ecosystem effects of fishing; develop expert system models to detect ecosystem changes (using indicators); compare ecosystem functioning over different periods and between systems; quantify trophic controls (bottom-up,top-down, wasp-waist); time-series analyses||Manage catches within productivity states/regimes, as identified using indicators of ecosystem state/ change
Benefit: optimisation of catches while keeping the risk low that catch levels will accelerate stock decline
|Fair potential for implementation of management response/ability to manage|
Fact Sheet by: EUR-OCEANS Knowledge Transfer Unit, hosted by the GLOBEC IPO at Plymouth Marine Laboratory.