Former Graduate Student
M.S. Biology 2014
Natal Tags can Elucidate Larval Dispersal in the Beach Spawning California Grunion, Leuresthes tenuis
Elements incorporated into larval otoliths have been used as natal tags to study population connectivity through larval dispersal in various marine species, but infrequently for open-coast species, and never for a beach spawning marine fish. To explore embryonic otoliths of the beach spawning fish Leuresthes tenuis as natal tags, Andy examined spatial variation of embryonic otolith chemistry at 15 beaches in the Southern California Bight (SCB) from Santa Barbara, CA to San Diego, CA. In addition, he examined the temporal stability of embryonic otolith chemistry from at least two separate spawning runs at three beaches (Topanga Canyon, Cabrillo, and Doheny). Otoliths were analyzed for five element to calcium ratios (Ba:Ca, Mg:Ca, Sr:Ca, U:Ca, and Mn:Ca) using laser-ablation inductively-coupled mass spectrometry (LA ICP-MS). The chemistry of embryonic otoliths was significantly different among sites and regions (MANOVA, p<0.0001). Discriminant function analysis (DFA) correctly assigned 41% of embryonic otoliths to their natal beach compared to 7% by chance (p=0.0002), and grouping sites into regions increased assignment success to 60% compared to 25% by chance. Embryonic otolith chemistry was not temporally stable (MANOVA, p<0.0001) at any of the three beaches examined. Andy’s results indicate that L. tenuis may be a potential target organism to examine population connectivity using natal tags, but application of this method would require sampling a larger proportion of source populations and would benefit from recent advances that apply spatial statistics. Consequently, embryonic otoliths could be used to test hypotheses about L. tenuis larval exchange in the SCB and across Point Conception, a major biogeographical barrier along the U.S. west coast.
Andy is currently working as a Marine Scientist at Tierra Data Incorporated in San Diego, CA.