98th ESA Annual Meeting (August 4 -- 9, 2013)

COS 123-8 - New and improved degree-days models for predicting when fish eggs will hatch in the field

Friday, August 9, 2013: 10:30 AM
L100D, Minneapolis Convention Center
Paul A. Venturelli and Fernanda Cabrini-Araujo, Fisheries, Wildlife, and Conservation Biology, University of Minnesota, St. Paul, MN
Background/Question/Methods

Lab and hatchery data show a clear relationship between egg development and incubation temperature in fish. Although this relationship is useful for predicting hatch date (DH) when incubation temperature is relatively constant, it is of little use when incubation temperature is variable (e.g., in flow-through hatcheries or the wild). In this study, we used published data to develop and evaluate degree-day models for predicting DH when incubation temperature is variable. These models rely on an estimate of the cumulative degree-days (CDD; oC*days) to hatch above some base temperature (Ti; oC). Our study was in two parts. In part 1, we used published relationships between days to hatch and incubation temperature to develop species-specific degree-day models. We then used published data to evaluate the ability of these models to predict DH in the field. In part 2, we developed alternative degree-day models for the species in part 1 by deriving empirical relationships between CDD, Ti, and the optimal temperature for egg development. We then determined the relative ability of these alternative models to predict DHin the field.

Results/Conclusions

We identified 64 fish species for which published data were available to develop species-specific degree-day models for predicting DH in the field. Published data were also available to evaluate model accuracy for 17 (27%) of these species. Across all species, our degree-day models were very accurate: ratio of predicted DH to observed DH 1.02±0.06 95% CI). Predicted DH was within 10% of observed DH for 14 of 17 species (82%). The largest errors in predicted DH occurred when observed DH was <20 days (i.e., for spring spawning species). In part 2 of our study, we found strong relationships between Ti estimate in part 1 and published estimates of optimal temperature for egg development (n = 55 species, r2 = 0.76), and between Ti and CDD estimated in part 1 (n = 63 species, r2 = 0.86). Degree-days models developed using these equations were only slightly less accurate than degree-day models from part 1, which suggests that this approach is a viable alternative. Overall, our results suggest that a degree-day approach that does not simply assume that Ti is zero can accurately predict DH the field.