2 results
Evaluating the performance of survey-based operational management procedures
- Marine Pomarede, Richard Hillary, Leire Ibaibarriaga, Johannes Bogaards, Panayiota Apostolaki
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- Journal:
- Aquatic Living Resources / Volume 23 / Issue 1 / January 2010
- Published online by Cambridge University Press:
- 17 March 2010, pp. 77-94
- Print publication:
- January 2010
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- Article
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The design and evaluation of survey-based management strategies is addressed in this article, using three case-study fisheries: North Sea herring, Bay of Biscay anchovy and North Sea cod, with a brief history and the main management issues with each fishery outlined. A range of operational management procedures for the case study stocks were designed and evaluated using trends that may be derived from survey indices (spawner biomass, year-class strength and total mortality) with an array of simple and more structured observation error regimes simulated. Model-free and model-based indicators of stock status were employed in the management procedures. On the basis of stochastic stock-specific simulations, we identified the following key determinants of successful management procedures: (i) adequate specification of the stock-recruit relationship (model structure, parameter estimates and variability), (ii) knowledge of the magnitude and structure of the variation in the survey indices, and (iii) explication of the particular management objectives, when assessing management performance. More conservative harvesting strategies are required to meet specified targets in the presence of increasing stochasticity, due to both process and observation error. It was seen that survey-based operational management procedures can perform well in the absence of commercial data, and can also inform aspects of survey design with respect to acceptable levels of error or bias in the surveys.
3 - Habitats
- Edited by Dave Checkley, Scripps Institution of Oceanography, University of California, San Diego, Jürgen Alheit, Yoshioki Oozeki, Claude Roy
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- Book:
- Climate Change and Small Pelagic Fish
- Published online:
- 08 January 2010
- Print publication:
- 20 August 2009, pp 12-44
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- Chapter
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Summary
Summary
The habitats of populations of small, pelagic fish, especially anchovy and sardine, in the Benguela, California, Humboldt, and Kuroshio-Oyashio current systems, and in the NE Atlantic, are described and discussed in regard to future climate change. These stocks have been the primary concern of the Small Pelagic Fish and Climate Change (SPACC) program of International GLOBEC. Each of these regions and stocks has a unique set of climate and ocean conditions and their variability. However, they also share common characteristics. Spawning and development occurs within broad ranges of temperature (12–26 °C) and salinity (<30–36) and in regions of high plankton production, associated with either upwelling or freshwater. Often, sardine are more oceanic and anchovy more coastal, often associated with wind-driven upwelling and rivers. Sardine tend to make longer migrations between spawning and feeding regions than do anchovy. The habitat of most populations of small, pelagic fish expands when the population size is large and contracts when it is small, often into refugia. Climate change may affect populations of small, pelagic fish by causing poleward shifts in distribution due to warming, some of which have already occurred. Other potential effects are due to changes in winds, hydrology, currents, stratification, acidification, and phenology.
Introduction
Small, pelagic fish, especially anchovy and sardine, abound in many, productive regions of the world ocean. Their habitats include areas with coastal and oceanic upwelling and freshwater influence and can be characterized by both geography (properties of the coast and bottom) and hydrography (properties of the water). The effects of climate change, be it of natural or anthropogenic origin, on populations of small, pelagic fish, are mediated by their habitats.