Choosing survey time series for populations as part of an ecosystem approach to fishery management

¹ Ifremer, Département EMH, BP 21105, 44311 Nantes, France
² CEFAS Lowestoft Laboratory, Pakefield Road, Lowestoft, Suffolk NR33 0HT, UK

Corresponding author: Verena.Trenkel@ifremer.fr

Received: 20 May 2008
Accepted: 3 July 2008

Abstract

Ecosystem assessments of fisheries based only on survey data will often have to use surveys that were designed historically for special purposes, e.g. for assessing abundances of two or three target species, or for tuning VPAs. An important question then is whether the previously collected data can provide informative time series of abundance indices and other state indicators for a wider range of target and non-target species. Some potential shortcomings of existing data series are treated in this paper leading to four questions which can guide the user to determine the suitability of an existing time series: did the survey cover the stock of each species adequately? Did survey catchability vary significantly between length or age classes? Did survey catchabilities vary significantly in space or time? Was the sampling effort sufficient? Simple methods for investigating these questions are proposed and illustrated with examples.