Historical spatial baselines in conservation and management of marine resources

Abstract

Increased knowledge on the spatial distribution of marine resources is crucial for the implementation of a true ecosystem approach to management and the conservation of marine organisms. For exploited fish species characterized by aggregation behaviour during spawning time, the identification and tracking of spawning areas is essential for a correct assessment of their productivity and population abundance. To elucidate this concept, we reconstructed the spatio-temporal distribution of adult plaice (Pleuronectes platessa, Pleuronectidae) during spawning time along the 20 th century. Historical data reveal that not only the abundance but also the former population richness was much higher than previously estimated and has declined because of protracted over-exploitation during the last 30years. We conclude that forecast of stock recovery to former levels of abundance neglecting spatial reorganizations might be over-optimistic and shaded by a lost memory of the past population richness. These results reinforce the importance of managing exploited marine resources at a greater spatial resolution than has been carried out in the history of fishery management. © 2010 Blackwell Publishing Ltd

Variability and connectivity of plaice populations from the Eastern North Sea to the Western Baltic Sea, and implications for assessment and management

“…It is important to notice that all these tagging data were old (up to 100 years) and may no longer be 198 representative for the current situation since population dynamics may have changed in relation to the 199 environmental conditions as shown in Cardinale et al (2011). Therefore, we conclude that these older data 200 provide a useful overall picture of the putative population structure, but do not allow any quantification of its 201 current dynamics.…”

“…There was an easterly net within-year flow towards the 168 Skagen peninsula as suggested by Cardinale et al (2011) or (2) a summer migration of fish spawning in the 170 westerly areas or in the North Sea towards feeding grounds in Skagerrak. Relative little mixing occured 171 between fish in the northern and southern Kattegat.…”

Long-term trajectory of some elasmobranch species off the Tuscany coasts (NW Mediterranean) from 50 years of catch data

“…Further fisheries management measures for fishing pressure reduction should be put in place, as highlighted by STECF Expert Working Group from the stock assessment on demersal resources in the Mediterranean (Cardinale et al 2011). While elasmobranchs should benefit from a further reduction in fishing effort, they are at the same time non-targeted (making a negligible part of fisherman intake) and resilient species with high post-capture survival rates.…”

“…However, this represents a broad category of elasmobranchs and probably includes more species, since it is not possible to accurately estimate the species composition. In this case the resolution of the series at species level is low but the use of the ISTAT-IREPA series greatly extends the time series and the possibility of identifying some baseline prior to the extensive trawling ef-fort development of the 1980s (Cardinale et al 2011). Yearly catch rates (kg/year/vessel) were calculated for each group.…”

“…The importance of using historical data to prevent misidentifying of baselines of abundance of marine resources is clear (Cardinale et al 2011); however, this comes with the price that historical data most often have lower resolution and higher uncertainty. Therefore, the compromise between accuracy and short time span versus low resolution but long time span needs to be carefully weighed.…”