Effects of temperature on somatic growth, otolith growth, and uncoupling in the otolith to fish size relationship of larval northern pike, Esox lucius L

Abstract

Verifying the link between somatic and otolith growth is crucial for a number of analyses that provide data on the ecology of early life stages of fish. In the current study, sagittal and lapillar otoliths were extracted from larval northern pike (n = 720) that were reared from eggs in RAS systems at three temperatures (10 °C, 15 °C, and 22 °C) for 28 days. The growth rate (SL at age) of larval northern pike was significantly dependent on rearing temperature with the highest rate observed at 22 °C (0.83 mm·d−1), a lower rate at 15 °C (0.48 mm·d−1), and the lowest at 10 °C (0.25 mm·d−1). The maximum value of growth observed for an individual larvae at a certain age was 1.28 mm·d−1. The higher somatic growth rate at higher temperatures was followed by faster lapillus and sagitta linear growth rates. Positive relationships between otolith growth and somatic growth were noted not only among temperatures but also within given temperatures. The sizes of lapilli and sagittae were strongly correlated with fish size, but both somatic growth and temperature had a statistically significant effect on those relationships. Magnitude of this phenomenon was however fish size dependent. We concluded that larval northern pike otoliths (both sagittae and lapilli) are a reliable source of information on somatic growth, and they can be used for increment trajectory width analysis and marginal otolith increment width analysis. However, if growth back-calculation is to be employed, it is recommended to consider the somatic growth and temperature effect on the fish size-otolith size relationship.