50
G. J. Pierce and J. Portela
on Cephalopod Life History and Fisheries (ICES 2008, 2009, 2010, 2011, 2012). Dunn
(1999) pointed to the value of simple techniques such as catch curves while several
authors have also utilised the Gomez-Muñoz model to estimate fishing effort for smallscale cephalopod fisheries (e.g. Rocha et al. 2006; Young et al. 2006b).
Traditional age-based methods are generally considered inappropriate for such
short-lived species and even if the approach could be adapted by changing the timescale to follow cohorts through the course of a year, age determination is probably
too time consuming to be carried out routinely for stock assessment (Ceriola and
Milone 2007; Arkhipkin and Shcherbich 2012). Unlike the case in many fish, the
high variability in cephalopod growth rates means that the use of age-length keys
is impractical.
Historically, production models (Roa-Ureta and Arkhipkin 2007), pre-recruit/recruit surveys and depletion models have all been used with some success (see Pierce
and Guerra 1994 for a review). However, the theoretical basis for using production
models is of questionable relevance to cephalopods: Environmental carrying capacity
is unlikely to be fixed due to the sensitivity of cephalopod population dynamics to
variation in environmental conditions and it is doubtful that clear stock–recruitment
relationships exist. Depletion methods work best in well-managed directed fisheries
such as the Falkland Islands squid fisheries (see, e.g. Beddington et al. 1990; Rosenberg et al. 1990; Basson et al. 1996; McAllister et al. 2004; Roa-Ureta and Arkhipkin
2007), where the licence system required on-board monitoring, allowing real-time assessment, with the possibility of fishery closure if escapement was estimated to have
fallen below a target value. In addition, the life cycle of the exploited species includes
a well-defined recruitment period, representing the start of the assessment period.
The absence of management measures for most European cephalopod fisheries
(apart from some restrictions on gear used and minimum landing size) reflects the
low importance attached historically to cephalopod fishing, the lack of attention
paid to nontraditional species and small-scale fishing, the impracticality of imposing catch quotas in by-catch fisheries and, possibly, the perception that cephalopods
are resilient to overfishing.
However, increased interest in targeting cephalopods in Europe means that even
small-scale coastal fisheries can no longer be assumed to be sustainable and, as
noted above, lessons from elsewhere in the world suggest that coastal cephalopod
species can be overexploited. Contingency plans are also needed to manage the
expected high level of interannual variation in landings. In addition, even if catch
quotas are unlikely to be useful, some safeguards need to be put in place even for
the difficult-to-manage by-catch fisheries. The options include:
• Protection of spawning areas. This is fundamental for coastal demersal and
benthic species which attach their eggs to the substrate. Experience in Portugal
shows that fixed gear such as trammel nets and traps can be an attractive site
for the attachment of loliginid squid eggs (A. Moreno, pers. comm.) and similar
issues arise for cuttlefish and octopus. Loss of eggs attached to gear could represent a serious problem for several stocks. In the Saharan Bank octopus fishery, it
has been suggested that coastal trap fishing impacts adversely on offshore trawl
fishing by removing mature females and eggs (Faraj and Bez 2007).
G. J. Pierce and J. Portela
on Cephalopod Life History and Fisheries (ICES 2008, 2009, 2010, 2011, 2012). Dunn
(1999) pointed to the value of simple techniques such as catch curves while several
authors have also utilised the Gomez-Muñoz model to estimate fishing effort for smallscale cephalopod fisheries (e.g. Rocha et al. 2006; Young et al. 2006b).
Traditional age-based methods are generally considered inappropriate for such
short-lived species and even if the approach could be adapted by changing the timescale to follow cohorts through the course of a year, age determination is probably
too time consuming to be carried out routinely for stock assessment (Ceriola and
Milone 2007; Arkhipkin and Shcherbich 2012). Unlike the case in many fish, the
high variability in cephalopod growth rates means that the use of age-length keys
is impractical.
Historically, production models (Roa-Ureta and Arkhipkin 2007), pre-recruit/recruit surveys and depletion models have all been used with some success (see Pierce
and Guerra 1994 for a review). However, the theoretical basis for using production
models is of questionable relevance to cephalopods: Environmental carrying capacity
is unlikely to be fixed due to the sensitivity of cephalopod population dynamics to
variation in environmental conditions and it is doubtful that clear stock–recruitment
relationships exist. Depletion methods work best in well-managed directed fisheries
such as the Falkland Islands squid fisheries (see, e.g. Beddington et al. 1990; Rosenberg et al. 1990; Basson et al. 1996; McAllister et al. 2004; Roa-Ureta and Arkhipkin
2007), where the licence system required on-board monitoring, allowing real-time assessment, with the possibility of fishery closure if escapement was estimated to have
fallen below a target value. In addition, the life cycle of the exploited species includes
a well-defined recruitment period, representing the start of the assessment period.
The absence of management measures for most European cephalopod fisheries
(apart from some restrictions on gear used and minimum landing size) reflects the
low importance attached historically to cephalopod fishing, the lack of attention
paid to nontraditional species and small-scale fishing, the impracticality of imposing catch quotas in by-catch fisheries and, possibly, the perception that cephalopods
are resilient to overfishing.
However, increased interest in targeting cephalopods in Europe means that even
small-scale coastal fisheries can no longer be assumed to be sustainable and, as
noted above, lessons from elsewhere in the world suggest that coastal cephalopod
species can be overexploited. Contingency plans are also needed to manage the
expected high level of interannual variation in landings. In addition, even if catch
quotas are unlikely to be useful, some safeguards need to be put in place even for
the difficult-to-manage by-catch fisheries. The options include:
• Protection of spawning areas. This is fundamental for coastal demersal and
benthic species which attach their eggs to the substrate. Experience in Portugal
shows that fixed gear such as trammel nets and traps can be an attractive site
for the attachment of loliginid squid eggs (A. Moreno, pers. comm.) and similar
issues arise for cuttlefish and octopus. Loss of eggs attached to gear could represent a serious problem for several stocks. In the Saharan Bank octopus fishery, it
has been suggested that coastal trap fishing impacts adversely on offshore trawl
fishing by removing mature females and eggs (Faraj and Bez 2007).