Abstract
Understanding how temperature affects the relative phenology of predators and prey is necessary to predict climate change impacts and recruitment variation. This study examines the role of temperature in the phenology of a key forage fish, the lesser sandeel (Ammodytes marinus, Raitt) and its copepod prey. Using time-series of temperature, fish larval and copepod abundance from a Scottish coastal monitoring site, the study quantifies how thermal relationships affect the match between hatching in sandeel and egg production of its copepod prey. While sandeel hatch time was found to be related to the rate of seasonal temperature decline during the autumn and winter through effects on gonad and egg development, variation in copepod timing mostly responded to February temperature. These two temperature relationships defined the degree of trophic mismatch which in turn explained variation in local sandeel recruitment. Projected warming scenarios indicated an increasing probability of phenological decoupling and concomitant decline in sandeel recruitment. This study sheds light on the mechanisms by which future warming could increase the trophic mismatch between predator and prey, and demonstrates the need to identify the temperature-sensitive stages in predator-prey phenology for predicting future responses to climate change.
Highlights
Understanding how temperature affects the relative phenology of predators and prey is necessary to predict climate change impacts and recruitment variation
The dates of peak spring abundance of the adult stage of C. helgolandicus were significantly correlated with the dates of peak spring abundance of Pseudocalanus sp (r = 0.58, p = 0.01) and Acartia clausi (r = 0.57, p = 0.02) but not Paracalanus parvus (r = 0.41, p = 0.1) and Temora longicornis (r = 0.32, p = 0.2)
Back-calculated dates of egg production were variable, with a maximum between day 38 and 72, while starting as early as day 14 and finishing as late as day 145; Fig. 1). These predictions are in agreement with the recorded presence of large naupliar stages in the zooplankton time series in the period corresponding to the back-calculated period of naupliar development in C. helgolandicus (Supplementary Fig. S1)
Summary
Understanding how temperature affects the relative phenology of predators and prey is necessary to predict climate change impacts and recruitment variation. The majority of studies that have considered changing phenology have either inferred changes from the temporal variability in the occurrence of a single taxa such as fish larvae or copepods[17,18,19] or compared general trends among trophic guilds across large spatial scales[20,21] Neither of these approaches is amenable to identifying the mechanisms that lead to trophic mismatch, as information relating to variability in both the predator and prey responses is required. In the northwest North Sea (ICES sandeel area SA4), sandeel recruitment variation could be explained by the degree of mismatch between Calanus helgolandicus egg production and sandeel hatch date[43] Whether this relationship indicates a strict link between the two species, or whether C. helgolandicus phenology covaries with that of a range of copepod prey species, still needs to be determined
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