Biophysical modelling of larval drift, growth and survival for the prediction of anchovy (Engraulis encrasicolus) recruitment in the Bay of Biscay (NE Atlantic)

Abstract

Fish recruitment is the result of the integration of small-scale processes affecting larval survival over a season and large oceanic areas. A hydrodynamic model was used to explore and model these physical-biological interaction mechanisms and then to perform the integration from individual to population scales in order to provide recruitment predictions for fisheries management. This method was applied to the case of anchovy (Engraulis encrasicolus) in the Bay of Biscay (NE Atlantic). The main data available to investigate survival mechanisms were past growth (otolith) records of larvae and juveniles sampled at sea. The drift history of these individuals was reconstructed by a backtracking procedure using hydrodynamic simulations. The relationships between (real) growth variation and variations in physical parameters (estimated by hydrodynamic simulations) were explored along the individual trajectories obtained. These relationships were then used to build and adjust individual-based growth and survival models. Thousands of virtual buoys were released in the hydrodynamic model in order to reproduce the space-time spawning dynamics. Along the buoy trajectories (representative of sub-cohorts), the biophysical model was run to simulate growth and survival as a function of the environment encountered. The survival rate after 3 months of drift was estimated for each sub-cohort. The sum of all these survival rates over the season constituted an annual recruitment index. This index was validated over a series of recruitment estimations. The modelling choices, model results and the potential use of the recruitment index for fisheries management are discussed.

Disentangling the effects of inherent otolith growth and model-simulated ecosystem parameters on the daily growth rate of young anchovies

“…Maillet & Checkley 1991, Baumann et al 2006a, Allain et al 2007. Recently, Hinrichsen et al (2010) used generalised additive model (GAM) analysis to compare daily increment widths with environmental parameters and identify the environmental factors that affect the growth rate of larval Baltic sprat Sprattus sprattus.…”

Climate change impacts on coastal and pelagic environments in the southeastern Bay of Biscay

“…Factors such as the NAO (albacore, Arregui et al 2006;sardine, Alheit & Hagen 1997; several fish stocks, mammals and seabirds, Hemery et al 2008), EA pattern (anchovy, Borja et al 2008); temperature anomaly (hake, Fernandes et al 2010), upwelling strength (anchovy, Borja et al 2008), turbulence (anchovy, mackerel and hake, Borja et al 1998, Allain et al 2007, Fernandes et al 2010, river discharge (anchovy, Planque & Buffaz 2008) and Ekman transport (anchovy, Irigoien et al 2008) have been shown to have significant effects on the recruitment or abundance of these species.…”

Growth of young-of-the-year European anchovy (<i>Engraulis encrasicolus</i>, L.) in the Bay of Biscay

“…A study by Cermeño et al (2008) found a maximum average increment width of 18 µm day -1 for the period of 40 to 60 days after hatching, similar to those measured in the present study. However, Allain et al (2003Allain et al ( , 2007 showed an average maximum growth increment of 12 µm day -1 for 40 to 50 days after hatching. Although the difference in otolith growth between these studies is evident, a comparison is not possible as the criteria employed by Allain et al (2003Allain et al ( , 2007 to interpret the otolith daily increment are unknown.…”

“…However, Allain et al (2003Allain et al ( , 2007 showed an average maximum growth increment of 12 µm day -1 for 40 to 50 days after hatching. Although the difference in otolith growth between these studies is evident, a comparison is not possible as the criteria employed by Allain et al (2003Allain et al ( , 2007 to interpret the otolith daily increment are unknown. However, it is likely that the observed difference between these studies is related to the different interpretation criteria.…”