1. Outi Heikinheimo Fish Pro II, Göteborg 14–16 February 2018
Stock-recruitment relationship of perch (Perca fluviatilis) in the Archipelago Sea, Finland
Outi Heikinheimo
Fish Pro II, Göteborg 14–16 February 2018

2. Perch catches and CPUEs Stock assessment Stock-recruitment models
Manuscript in prep.: Stock-recruitment relationship in perch (Perca fluviatilis): effects of water temperature and pikeperch (Sander lucioperca) in the Archipelago Sea, southwestern Finland.   Eevi Kokkonen*, Outi Heikinheimo, Anssi Vainikka, Zeynep Pekcan-Hekim
Perch catches and CPUEs
Stock assessment
Stock-recruitment models
Environmental variables

4. Perch catches 1980 – 2016

5. Commercial perch catch 1980 - 2016

6. Stock assessment (Virtual Population Analysis VPA)
Data: Catch statistics, annual samples from commercial catches.
Age structure, mean weights at age => Annual catches in numbers of perch
VPA calculates the population size and fishing mortality 2 3 4 5 6 7 8 9 10
…………………………………………2009 F
RECRUITS
POPULATION
SIZE BY AGE
Age

7. Year-class strength of perch vs. pikeperch population size (ages ≥ 1)
June –July temp

8. Perch stock was on a high level from 1993 to 2002

9. Catches per unit of effort in gillnet fishing

10. Spawning stock – recruitment (without environmental variables)

12. Testing models with different variables

13. Predictions with different models, June-July temperature and pikeperch stock included

14. Conclusions
Recruitment of perch is determined by summer temperature, spawning stock size and the abundance of pikeperch
The assumed effect of pikeperch is supported by literature from Finnish lakes and relative species in North America (yellow perch and walleye)
Most probably predation, but competition might be involved, too
However, there are other rather simultaneous changes in the environment
Increased areas suffering from oxygen deficiency
Increased abundance of Cyprinid fish, no monitoring data