| Summary: | 碩士 === 國立臺灣大學 === 海洋研究所 === 107 === Understanding the effects of temperature on length of larval durations (a.k.a. pelagic larval durations, PLDs) provides insight into larval survival, dispersal distance, and ultimately, population persistence. Previous research suggests a nonlinear relationship between the PLDs and temperature for tropical reef fishes: i.e., rising temperature tends to shorten PLDs, but beyond the thermal optima (the temperature corresponding to the shortest PLD) further increases in temperature will lead to extended PLDs. However, such relationships are unclear for subtropical reef fishes. Given that the upper limit of temperature in the subtropical region exceeds the thermal optima of some tropical fishes and that most subtropical reef fishes spawn all-year-around, we hypothesized a nonlinear effect of temperature on PLDs for subtropical reef fishes. To test this hypothesis, we compared PLDs with two temperature indices during PLDs (average temperature and growing degree-day (GDD12 or 15) for five common reef fishes collected from tidal pools at the northern coast of Taiwan throughout a year. We found that these species displayed differential sensitivities to either of temperature indices: i.e., PLDs of two species were sensitive to GDD15 (Abudefduf vaigiensis and Istiblennius edentulus), while those of the other three species were sensitive to average temperature (Ostorhinchus cookii, Abudefduf sordidus, Bathygobius fuscus). Furthermore, a linear (negative) effect of temperature (indexed by average temperature) on PLDs was found for the Bathygobius fuscus, as opposed to nonlinear effects of temperature for the other four species. Most importantly, we found that temperatures have surpassed thermal optima for three species: Abudefduf vaigiensis, Istiblennius edentulus, and Ostorhinchus cookii. A positive or nonlinear effect of temperature on PLDs indicates a negative impact on recruitment for subtropical reef fishes under warming.
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