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Report2013Open access

Waking the Deads : final report

Sundelöf, Andreas; Bartolino, Valerio; Cardinale, Massimiliano

Abstract

The shifting baseline syndrome has changed our perception of demographic struc-ture, population abundance and distribution of commercially exploited fish popula-tions. The targeting and selective behavior of fisheries did affect not only the abun-dance of fish stocks but also their age structure, spatial distribution and life history traits. Harvesting diminish the probability of survival, changing the size structure of the population. A size selective fishery targeting large fish will reduce the propor-tion of large individuals compared to a natural population size structure. At larger sizes, females of many species of fish produce disproportionately more eggs, and in many cases larger females produce eggs of better quality. Thus local size structure likely heavily influences local productivity. Natal homing results in spatial structuring that strongly influences regional productivity. To determine spatial baselines for fisheries management spatially structured data back in time are required. Productivity on a regional scale is de-pendent on local demography and spatial persistence of the different stock compo-nents. Spatial structure allows for genetic structuring and local adaptations that may also contribute to local and regional productivity. Spatial baselines, as developed for several species through this project, set the scale on which stocks should be assessed and thus management applied. This project analyzed a unique set of historical survey data that was contrasted with data on landings. We addressed the major topics of changes in abundance over time, spatial distribution, and climatic forcing. In the project we modeled the abun-dances and the spatial distribution of populations over time of several commercial and non-commercial species and suggested spatial baselines for the management units of several stocks in the Kattegat and Skagerrak. Understanding the mechanisms driving the spatial dynamics of fish populations is crucial for the management of exploited resources and ecosystems. The four different Work Packages (changes in abundance over time, spatial distribution, climatic forcing, and spatial patterns by otolith chemistry) aimed at the identifica-tion of spatial structure of fish stocks for management purposes and resolving the dependence of exploited fish stocks on different biotic and abiotic factors. The substantial difference in stock status described by several of the publications (6 scientific contributions and 5 manuscripts) emerging from this project highlights the general importance of the historical perspective for managing natural resources. For example, spatial modeling of abundance of plaice (Pleuronectes platessa) and turbot (Scopthalmus maximus) revealed several spawning aggregations and rede-signed the spatial structure of the species between the North Sea and the Western Baltic zones. Also we have shown a desegregation of the spatial structure of ga-doids and a great decline in population size over time of haddock (Melanogrammus aeglefinus), pollack (Pollachius pollachius) and cod (Gadus morhua).

Published in

Aqua reports
2013, number: 2013:15eISBN: 978-91-576-9177-4Publisher: Department of Aquatic Resources, Swedish University of Agricultural Sciences