A generalized simple bioenergetic model was used to estimate consumption of European hake in both north- and southern stocks for the period 1994-2008. Consumption in biomass was estimated from weight-at-age data and growth parameters and then converted to energy intake in kJ using the prey-preference by size in percentage obtained from stomach contents and the energy-prey conversion factors. The energy consumption in kJ was then estimated for each year and for a range of hake between 1 and 75 cm. The consumptions from bioenergetic models were adjusted to the observed consumption from stomach content and then fitted to the theoretical maximum possible consumption model. Results showed that from the simple bioenergetic analyses smaller hake consumes slightly lower energy, while for individuals larger than 60 cm the model shows a greater consumption. For northern stock the estimated consumption for an individual hake of 50 cm shows an important variation with high values at the beginning of the time series (above 25000 kJ), although with a clear and sharp decreasing trend. In the last period consumption considerably fluctuated with a minimum of 21600 kJ in 1998 and a maximum of 30000 kJ in 2001. The source of variation in annual consumption was studied correlating the values with several indices of potential preys (anchovy, blue whiting and horse mackerel). The best fit was obtained with the survey indices of horse mackerel 0-group which showed a similar trend in abundance. Horse mackerel catch in number-at-age-0 showed a correlation of 0.89 with estimated total consumption from bioenergetic model and a correlation of 0.78 with the m0 parameter in the maximum possible consumption model. For the southern stock, consumption shows an important variation with values at the beginning of the time series around 25000 kJ, decreasing until 1997, then a sharp increase in consumption is observed in 1998, 1999 and 2000, followed with a clear and sharp decreasing trend, until reach the minimum in 2002. In this case the best fit was obtained with the survey indices of blue whiting abundance which showed a similar trend in abundance as consumption with a correlation of 0.79 with estimated total consumption from bioenergetic model and a correlation of 0.81 with the m0 parameter in the maximum possible consumption model. These results indicate that growth in hake is very much dependent on young horse mackerel for northern stock and on blue whiting for southern stock, which is coincident with preferred preys observed in stomach content demonstrating the validity of this method to estimate consumption from weight-at-age data

International Symposium on the Biology, Harvesting, Management and Conservation of Hakes, Portland, 11-12 May 2010

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