Issues of ecosystem-based management of forage fisheries in “open” non-stationary ecosystems: the example of the sardine fishery in the Gulf of California

Abstract

The Gulf of California system presents major challenges to the still developing frameworks for ecosystem-based management (EBM). It is very much an open system and is intermittently subject to important influxes of migratory visitors, including large pelagic predatory fishes and small pelagic forage fishes. These migrants include the more tropical species from the coastal ecosystems to the south and perhaps subtropical sardines and anchovies from the California Current upwelling system. In addition to the multi-annual ENSO-scale and what may seem to be rather erratic episodes of major population incursions, the Gulf presents nonstationary, transient aspects on a variety of longer time scales. Moreover, the removal of top predators by commercial and sport fisheries has introduced trends that must be affecting the entire ecosystem, and certainly the forage fishes that are their major prey base. In addition to size limits, fishing seasons, area closures and license limitations, the fishery is managed by an ad hoc adaptive management system, in which the fishing season can be shortened or additional areas closed to fishing if pre-season exploratory fishing surveys indicate a shortage of small pelagic fishes on the fishing grounds. Whether this system is likely to be sustainable in the long term is difficult to determine, given the potential for rapid changes in the system because of environmental changes and/or feedbacks within the food web. Thus it appears that innovative management frameworks, among other things utilizing the comparative method, may be required in order to determine defensible tradeoffs between precaution and resource utilization.

Exploring the microzooplankton–ichthyoplankton link: a combined field and modeling study of Atlantic herring (Clupea harengus) in the Irish Sea

“…It is clear that a variety of physical and biological processes can interact to affect recruitment strength in clupeids and other fishes (Houde, 2008) and that the dominant process(es) may not be stationary (Bakun et al, 2010). Nonetheless, having sufficient prey resources during early larval life will always be a necessary prerequisite for the growth and survival of the larvae of clupeids and other fishes.…”

Strictly for the birds?

“…When the sardine stock is in good condition, it probably is the largest single fish stock in the Northeast Pacific Ocean. It is thought to play a crucial role in the California current 4 ecosystem as forage for a multitude of species higher up in the food chain [8]. Given this critical role, one would expect the sardine collapse to have caused a severe decline of fish stocks higher up in the food chain.…”

“…Hence, when the stocks of these fish are at low levels, the amount of biomass transferred further up in the food chain could be severely limited. This has given rise to the "wasp-waist" metaphor as a description of an ecosystem critically dependent on a few strategic species in the middle of the food chain [3,4], but the relevance of this metaphor is not uncontested [5]. A recent review of the role of forage fish puts it this way ( [4] p. 12):…”

Review of Long Term Macro-Fauna Movement by Multi-Decadal Warming Trends in the Northeastern Pacific

“…It is a key component of the California Current pelagic ecosystem, being the main prey of several pelagic species such as seabirds, marine mammals, predatory fishes and squid (Bakun et al, 2010). This sardine has two core centers of distribution, one in the west coast of the Baja California Peninsula, and the other inside the Gulf of California.…”