Climate change has negative effects on fish recruitment

HEDSTRÖM, PER; RODRÍGUEZ, PATRICIA; VASCONCELOS, FRANCISCO; JAN KARLSSON; BYSTRÖM, PÄR

Londres

Conferencia; INTECOL; 2013

In temperate climates, years with strong fish recruitment in both marine and freshwater systems have been correlated to high water temperature during the first growth season. This has been suggested to be related to temperature dependent higher growth rates of YOY fish. Whether increased water temperature results in elevated growth or not depends on the resource availability, suggesting a relationship between individual gain and recruitment mediated via the interplay between resource levels and temperature. Ongoing climate change is predicted to increase water temperature and, via increased precipitation, export of terrestrial Dissolved Organic Carbon (DOC) which generally is argued to decrease system productivity and fish production.   In an outdoor clear water experimental pond (16 enclosures, 10×8 m, depth 1.6m) with natural benthic and pelagic primary producers and consumers, we tested the effects of temperature (+3ºC to natural temperature development) and increased natural DOC concentration (+4 mg/l) in a factorial design on recruitment (growth, density and biomass) of three-spined sticklebacks. In May 40 adult sticklebacks were introduced in each enclosure and size structure, density and biomass of the recruitment were estimated in October. Nutrient concentrations, primary production, zooplankton and zoobenthos densities were sampled continuously.   Increased temperature had little effects on growth and size structure but had strong negative effect on recruitment, both in numbers and biomass, while increased DOC concentration had no effect on stickleback recruitment. Lower gross primary production and resource levels (zooplankton and zoobenthos) in combination with higher metabolic costs are suggested to be the main reasons for the negative effects of increased temperature on recruitment.      Based on our results, we suggest that future progress of climate change may, counter intuitively, have negative effects on fish recruitment due to temperature dependent increase in energy requirements in fish in relation to the net effects on ecosystem productivity.