A two-stage biomass model to assess the English Channel cuttlefish (Sepia officinalis L.) stock

Abstract

The English Channel cuttlefish (Sepia officinalis) is the most abundant cephalopod resource in the Northeast Atlantic and one of the three most valuable resources for English Channel fishers. Depletion methods and age-structured models have been used to assess the stock, though they have shown limitations related to the model assumptions and data demand. A two-stage biomass model is, therefore, proposed here using, as input data, four abundance indices derived from survey and commercial trawl data collected by Ifremer and Cefas. The model suggests great interannual variability in abundance during the 17 years of the period considered and a decreasing trend in recent years. Model results suggest that recruitment strength is independent of spawning–stock biomass, but appears to be influenced by environmental conditions such as sea surface temperature at the start of the life cycle. Trends in exploitation rate do not reveal evidence of overexploitation. Reference points are proposed and suggestions for management of the sustainable utilization of cuttlefish in the English Channel are advanced.

Interactive Governance for Small-Scale Fisheries

“…Nonetheless, new assessment approaches are currently being refi ned and trialed for EU cephalopod stocks (see ICES 2014 ), including the use of production models which incorporate environmental effects, and population biomass models (Gras et al 2014 ). Although wide fl uctuations in abundance occur (typically averaging around 40 % a year), studies in Galicia (Spain) suggest that abundance of the upcoming cohort is potentially highly predictable based on knowledge of environmental conditions (Otero et al 2008 ).…”

The survival of discarded Sepia officinalis in the English Channel

“…In European waters, cuttlefish are among the most important commercial cephalopod resource (Denis & Robin 2001;Pierce et al 2010) and are currently the highest yielding cephalopod group harvested in the north-east Atlantic (Royer et al 2006). However, landings of the common cuttlefish S. offcinalis dominate, with the English Channel (International Council for Exploration of the Seas (ICES) division VIId and VIIe) supporting the main fishery for this species (Royer et al 2006;Gras et al 2014). However, landings of the common cuttlefish S. offcinalis dominate, with the English Channel (International Council for Exploration of the Seas (ICES) division VIId and VIIe) supporting the main fishery for this species (Royer et al 2006;Gras et al 2014).…”

“…Using a combination of different metiers, including beam trawling, otter trawling and coastal trapping, cuttlefish are targeted at nearly every phase of their life cycle (Denis & Robin 2001;Pierce et al 2010;Gras et al 2014). Using a combination of different metiers, including beam trawling, otter trawling and coastal trapping, cuttlefish are targeted at nearly every phase of their life cycle (Denis & Robin 2001;Pierce et al 2010;Gras et al 2014).…”

“…Recent models suggest that survival of juveniles is of more importance than spawning stock biomass in terms of recruitment strength and stock abundance in English Channel cuttlefish (Gras et al 2014). Offshore fishing is concentrated in the centre of the Channel with a peak between November and March (ICES2003; Gras et al 2014), coinciding with the known migration pattern of this population (Boucaud-Camou & Boismery 1991). Offshore fishing is concentrated in the centre of the Channel with a peak between November and March (ICES2003; Gras et al 2014), coinciding with the known migration pattern of this population (Boucaud-Camou & Boismery 1991).…”

The use of Depletion Methods to assess Mediterranean cephalopod stocks under the current EU Data Collection Framework

“…The EU Data Collection Framework (DCF) for national fishery data collection programmes (EU, 2000(EU, , 2008 includes some provision for the collection of biological data and fishery statistics of cephalopods in areas such as the North East Atlantic and the Mediterranean. However, in spite of these efforts, little has been done to assess European cephalopod stocks, and most existing studies have been focussing on the English Channel and Scottish waters (Young et al, 2004;Challier et al, 2005a;Royer et al, 2006;Gras et al, 2014).…”