The Blackspot Seabream (Pagellus bogaraveo) fishery is a clear example of the
influence of the aforementioned factors on the abundance variability (Báez et al.
2014; Gutiérrez-Estrada et al. 2017; Sanz-Fernández et al. 2019). This species, found
from the south of Norway to the Canary Archipelagos in the Atlantic Ocean and in
the Mediterranean Sea basin (Desbrosses 1938), is one of the main exploited
resources in the Strait of Gibraltar. This protandric hermaphrodite species lives in
a depth range that varies between the surface and 700 m and is the target species in
this area of two artisanal fleets belonging to two countries with very different fishing
policies developing their fishing activity in a small area characterized by a high
environmental complexity (Gil 2006; Czerwinski 2008). In this context there is no
ideal methodology to manage and apply all available information and to provide an
exact resource assessment, and therefore, the use of complementary procedures that
allow to reduce the uncertainty associated to the obtained estimations is advisable.
Thus, it would be possible to carry out an integrated management and ecosystem
planning focused on the sustainability of the resource.
Therefore, this chapter describes the different approaches to assess the abundance
of the Blackspot Seabream population in the Strait of Gibraltar. This way, using the
joint data from Morocco and Spain, one classic method and two novel approaches
were used to evaluate the current status of the stock. The first was based on the length
cohort analysis (LCA) and virtual population analysis (VPA): from the obtained
results, a yield per recruit (YpR) analysis was run to estimate ad hoc reference points
(F MAX and F 0.1 ). The second approach was carried out using the globally applicable
area disaggregate general ecosystem toolbox (Gadget) model developed by Begley
and Howell (2004), and finally the third approach was obtained by means of the
SimFish methodology proposed by Gutiérrez-Estrada et al. (2017).
19.2 Description of the Fleets, Stock Identification,
and Landings
The Blackspot Seabream is one of the principal demersal species targeted in the
Strait of Gibraltar for its highest commercial value compared to other demersal
resources. The Spanish fishery targeting the Blackspot Seabream has been developing along the Strait of Gibraltar area since the earliest 1980s. This is an almost
monospecific fishery, with one clear target species which represents 74% of the total
landed species (Silva et al. 2002). The main harbors are located in Tarifa and
Algeciras (Spain) and Tangier (Morocco). Less important landings are also carried
out at Conil and Ceuta ports (Spain).
In Spain the main fishing hook gear used is known as “voracera” (Gil 2006;
Czerwinski 2008), although occasionally this species is also caught by means of
traditional longliners. The “voracera” is a local mechanized handline baited with
sardine. Fishing is carried out taking advantage of the turnover of the tides in
bottoms from 300 to 600 m depth. Every boat uses a maximum of 30 lines per day
630
J. Gil-Herrera et al.
influence of the aforementioned factors on the abundance variability (Báez et al.
2014; Gutiérrez-Estrada et al. 2017; Sanz-Fernández et al. 2019). This species, found
from the south of Norway to the Canary Archipelagos in the Atlantic Ocean and in
the Mediterranean Sea basin (Desbrosses 1938), is one of the main exploited
resources in the Strait of Gibraltar. This protandric hermaphrodite species lives in
a depth range that varies between the surface and 700 m and is the target species in
this area of two artisanal fleets belonging to two countries with very different fishing
policies developing their fishing activity in a small area characterized by a high
environmental complexity (Gil 2006; Czerwinski 2008). In this context there is no
ideal methodology to manage and apply all available information and to provide an
exact resource assessment, and therefore, the use of complementary procedures that
allow to reduce the uncertainty associated to the obtained estimations is advisable.
Thus, it would be possible to carry out an integrated management and ecosystem
planning focused on the sustainability of the resource.
Therefore, this chapter describes the different approaches to assess the abundance
of the Blackspot Seabream population in the Strait of Gibraltar. This way, using the
joint data from Morocco and Spain, one classic method and two novel approaches
were used to evaluate the current status of the stock. The first was based on the length
cohort analysis (LCA) and virtual population analysis (VPA): from the obtained
results, a yield per recruit (YpR) analysis was run to estimate ad hoc reference points
(F MAX and F 0.1 ). The second approach was carried out using the globally applicable
area disaggregate general ecosystem toolbox (Gadget) model developed by Begley
and Howell (2004), and finally the third approach was obtained by means of the
SimFish methodology proposed by Gutiérrez-Estrada et al. (2017).
19.2 Description of the Fleets, Stock Identification,
and Landings
The Blackspot Seabream is one of the principal demersal species targeted in the
Strait of Gibraltar for its highest commercial value compared to other demersal
resources. The Spanish fishery targeting the Blackspot Seabream has been developing along the Strait of Gibraltar area since the earliest 1980s. This is an almost
monospecific fishery, with one clear target species which represents 74% of the total
landed species (Silva et al. 2002). The main harbors are located in Tarifa and
Algeciras (Spain) and Tangier (Morocco). Less important landings are also carried
out at Conil and Ceuta ports (Spain).
In Spain the main fishing hook gear used is known as “voracera” (Gil 2006;
Czerwinski 2008), although occasionally this species is also caught by means of
traditional longliners. The “voracera” is a local mechanized handline baited with
sardine. Fishing is carried out taking advantage of the turnover of the tides in
bottoms from 300 to 600 m depth. Every boat uses a maximum of 30 lines per day
630
J. Gil-Herrera et al.