males that progressively develop their female gonads to become functional females;
therefore it is necessary to know the relationship between length and the proportion
of males and functional females. Also, an estimation of the natural mortality and the
biomass of age class 0+ at the moment t ¼ 0 is required (a complete and detailed
description of the parameters required and the algorithms can be found in GutiérrezEstrada et al. 2017; Sanz-Fernández et al. 2019 and Gutiérrez-Estrada et al. 2020).
To simulate the abundance of Blackspot Seabream, SimFish requires the catch
time series on a monthly scale. In this case, the catches of the Spanish and Morocco
are considered jointly. If, in addition to evaluating the abundance or biomass of the
population, we want to evaluate the effect of environmental variables, SimFish will
require a different environmental database composed of historical series of oceanographic and climate indices.
Initially, the simulations of the Blackspot Seabream fishery in the Strait of
Gibraltar were carried out under stability conditions, that is, in absence of catches
and considering no effects of environmental conditions on the variation of biological
parameters. This provided baseline simulations that allowed to obtain initial values
Fig. 19.8 (continued)
19 The Blackspot Seabream Fishery in the Strait of Gibraltar: Lessons and. . .
647
therefore it is necessary to know the relationship between length and the proportion
of males and functional females. Also, an estimation of the natural mortality and the
biomass of age class 0+ at the moment t ¼ 0 is required (a complete and detailed
description of the parameters required and the algorithms can be found in GutiérrezEstrada et al. 2017; Sanz-Fernández et al. 2019 and Gutiérrez-Estrada et al. 2020).
To simulate the abundance of Blackspot Seabream, SimFish requires the catch
time series on a monthly scale. In this case, the catches of the Spanish and Morocco
are considered jointly. If, in addition to evaluating the abundance or biomass of the
population, we want to evaluate the effect of environmental variables, SimFish will
require a different environmental database composed of historical series of oceanographic and climate indices.
Initially, the simulations of the Blackspot Seabream fishery in the Strait of
Gibraltar were carried out under stability conditions, that is, in absence of catches
and considering no effects of environmental conditions on the variation of biological
parameters. This provided baseline simulations that allowed to obtain initial values
Fig. 19.8 (continued)
19 The Blackspot Seabream Fishery in the Strait of Gibraltar: Lessons and. . .
647