Article ; Online: Relations Between Abiotic and Biotic Environmental Variables and Occupancy of Delta Smelt (Hypomesus transpacificus) in Autumn
Estuaries and Coasts. 2023 Jan., v. 46, no. 1 p.149-165
2023
Abstract: There is much debate about the extent to which water management in the upper San Francisco Estuary, California, affects the habitat and status of delta smelt (Hypomesus transpacificus), an endemic fish protected under the US and California Endangered ... ...
| Abstract | There is much debate about the extent to which water management in the upper San Francisco Estuary, California, affects the habitat and status of delta smelt (Hypomesus transpacificus), an endemic fish protected under the US and California Endangered Species Acts. For example, current management reflects the hypothesis that salinity, and in some cases the location of the tidally averaged salinity of 2 parts per thousand (X2), is a reliable indication of habitat quality. We evaluated hypotheses about environmental drivers of the quality of delta smelt habitat (probability of occupancy) during autumn that were developed by experts on the species and estuary. We fit Bayesian occupancy models, which account for imperfect detection, and identified those that best predicted the presence of delta smelt in catch data from 1980 to 2015. The most strongly supported model indicated that occupancy was associated with salinity (measured as specific conductance) and temperature, and detection was associated with body size, sample volume, water clarity, and tidal stage. The second most strongly supported model indicated that occupancy was associated with the abundance of a hypothesized competitor, threadfin shad (Dorosoma petenense), an expert-elicited index of predation intensity, and water clarity, and detection was associated with body size, sample volume, water clarity, and time of day. Our results suggested that clarity did not affect occupancy, but affected finer-resolution processes of local presence and detection at sampling stations. Spatial patterns in occupancy were consistent in wet and dry years, suggesting that management on the basis of salinity oversimplifies estimation of habitat quantity and quality. |
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| Keywords | Bayesian theory ; Dorosoma petenense ; Hypomesus transpacificus ; autumn ; body size ; estuaries ; habitats ; indigenous species ; models ; predation ; probability ; salinity ; temperature ; water management ; water quality ; California |
| Language | English |
| Dates of publication | 2023-01 |
| Size | p. 149-165. |
| Publishing place | Springer US |
| Document type | Article ; Online |
| ZDB-ID | 2229170-2 |
| ISSN | 1559-2731 ; 1559-2723 |
| ISSN (online) | 1559-2731 |
| ISSN | 1559-2723 |
| DOI | 10.1007/s12237-022-01100-x |
| Database | NAL-Catalogue (AGRICOLA) |
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