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Presented by : Michael Ballón

Trends in relative investment of energy in growth and/or reproduction by Peruvian hake Merluccius gayi peruanus from 1972 – 2004: an issue of length dependence. Presented by : Michael Ballón. Instituto del Mar del Peru, Project INCOFISH.

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Presented by : Michael Ballón

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  1. Trends in relative investment of energy in growth and/or reproduction by Peruvian hake Merluccius gayi peruanusfrom 1972 – 2004: an issue of length dependence Presented by: Michael Ballón Instituto del Mar del Peru, Project INCOFISH Authors: Michael Ballón, Claudia Wosnitza-Mendo, Arnaud Bertrand, Jacqueline Palacios, Humberto Olivera, and Renato Guevara-Carrasco

  2. OVERVIEW Introduction Objective Materials and Methods Results and Discussion Conclusions

  3. Introduction • Significance of hake • Distribution • Main factors that have affected the hake population • sardine and anchovy regime • El Niño • Overfishing 40 cm  25 cm • Current situation • New regulations (2002) were set up based on a single species approach (IMARPE) • The stock still far from recovery • Why?

  4. Objective Hake physiological responses Main question: How has hake reacted physiologically to the fishing pressure and the physical environment? Clarifying the effects. Reducing uncertainty about: Natural Mortality and Recruitment Success

  5. Materials and Methods Biological data: 52106 Female hakes sampled from 1971-2004 from Paita port Total body weight (W) Total length (L) Gonad weight (Wg) Stomach weight (Ws) Biological Indices Fulton's condition factor K = W.L-3 Gonadosomatic index GI = Wg.W-1 Fullness index FI = Ws.W-1 Physical environment and time Paita sea surface temperature anomaly (SSTA) Year-Month (YM) Time series (1971-2004) Condition factor Gonadosomatic index

  6. Results and Discussion…time series

  7. Results and Discussion…time series Long term Upward trend in condition factor Downward trend in reproduction activity Short term Negative impact of El Niño In both: Fish condition and reproduction

  8. Results and Discussion…? What are the factors that influence fish condition and maturation proccess?

  9. Materials and Methods Biological data: 52106 Female hakes sampled from 1971-2004 from Paita port Total body weight (W) Total length (L) Gonad weight (Wg) Stomach weight (Ws) Biological Indices Fulton's condition factor K = W.L-3 Gonadosomatic index GI = Wg.W-1 Fullness index FI = Ws.W-1 Physical environment and time Paita sea surface temperature anomaly (SSTA) Year-Month (YM) Generalized Additive Model GAM (1980 -2004) Large hakes (35-50 cm)Small hakes (20-35 cm) Condition factor K according to GI+FI+SSTA+YM Gonadosomatic index GI according to K+FI+SSTA+YM

  10. Better condition “Condition factor” More food Gonadosomatic index Fullness index Results and Discussion…GAM models Condition factor: K according to GI+FI+SSTA+YM Large hake (35-50cm) Small hake (20-35cm) During the spawning season there is a starving process. Fecundity depends more on the initial condition factor than on the food intake during the spawning season. Gonadosomatic Index: GI according to K+FI+SSTA+YM Starving Higher Fecundity Better condition

  11. EL Niño + _ Results and Discussion… Large Large “Gonadosomatic index” “Condition Factor” Small Small SSTAnomaly SSTAnomaly Poor condition + spawning  high mortality Large hake invest more energy in reproduction than small hake Large hake disappeared during the El Niño 1992-93 and 1997-98

  12. Small hake (20-35 cm) “Condition factor” “Gonadosomatic index” RESULTS and DISCUSSION…long term Large hake (35-50 cm) ? “Gonadosomatic index” “Condition factor” Why small hake spent their energy reserves in reproduction and large hake do not, although the latter has a higher condition factor ?

  13. RESULTS and DISCUSSION…long term Is this a density-dependent effect? • Low reproduction could be expected when biomass is close to the carrying capacity level • HOWEVER • hake biomass has been at a low level from the late 1990s onwards • Size at first maturity has reduced in the last decades (recovering SSB) • AND at the same time large hake has reduced reproduction activity • That is not a logical density-dependent effect

  14. + _ + _ + _ 2 cm 2 cm 2 cm RESULTS and DISCUSSION…long term 35 • Sex proportion from 80% males to 80% females • Lack of males for large hake ( >35 cm) • Low fertilization rate • Low stimulation for the spawning act Female proportion 25 Female propotion estimated from commertial landings Paita 20 Years

  15. Conclusions

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