Biochemical Identification and Assessment of Population Subdivision in Morphologically Similar Native and Invading Smelt Species (Hypomesus) in the Sacramento-San Joaquin Estuary, California

TitleBiochemical Identification and Assessment of Population Subdivision in Morphologically Similar Native and Invading Smelt Species (Hypomesus) in the Sacramento-San Joaquin Estuary, California
Publication TypeJournal Article
Year of Publication1998
AuthorsTrenham, P. C., H. Shaffer B., & Moyle P. B.
JournalTransactions of the American Fisheries Society
Volume127
Issue3
Pagination417-424
AbstractThe invasion of the Sacramento-San Joaquin estuary by the wakasagi Hypomesus nipponensis poses threats of competition and hybridization with the endemic delta smelt Hypomesus transpacificus, a species listed as threatened by federal and state agencies. Small individuals of these species are difficult to distinguish morphologically, but correct identification is extremely important to avoid mistaking delta smelt for wakasagi under the limited take provisions of the federal endangered species act. Allozyme markers were used to identify 280 individual fish from several sites across the range of H. transpacificus. We used these results to document the current level of invasion by H. nipponensis, quantify levels of misidentification based on morphological characters, identify hybrid individuals, and estimate levels of gene flow in H. transpacificus. Wakasagi have spread throughout the Sacramento-San Joaquin estuary, and further monitoring will be necessary to determine the long-term consequences of their invasion on the native delta smelt. Our data suggest that when the level of uncertainty in morphological identification is high, biochemical identification is the safest way to identify fish. We identified only two F1 hybrid individuals, suggesting that although hybridization does occur, it is not a serious threat to delta smelt at the present time. Finally, estimates of θ based on four variable allozyme loci indicate that gene flow between our four sampled locations is very high in H. transpacificus.
URLhttp://dx.doi.org/10.1577/1548-8659(1998)127<0417:BIAAOP>2.0.CO;2
DOI10.1577/1548-8659(1998)127<0417:BIAAOP>2.0.CO;2