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INVESTIGATING THE EFFECTS OF ALGAL TURBIDITY ON MATING SYSTEM OF THE DWARF SEAHORSE (HIPPOCAMPUS ZOSTERAE)**

Abstract

Dwarf seahorses (Hippocampus zosterae) are an excellent environmental indicator species because they spend their entire lives in coastal communities that are threatened by human-induced eutrophication. The goal of this study was to quantify laboratory reproductive success and identify the mate preferences in clear vs turbid treatments. The experimental design included paired (1F:1M), female-biased (2F:1M), and male-biased (1F:2M) treatments, in clear and turbid waters with a total of 128 seahorses across 8 replications. Of the 48 potential matings, the study yielded 40 males with reproductive success, 7 with brood reductions, and 1 non-mating. Mating latency was shorter for turbid treatments compared to their respective treatments in clear water. There was no detectable effect of algal turbidity on reproductive success, but differences were seen among the three treatments of varying sex ratios, with brood sizes being the highest in the female biased treatment (28 ± 4.56), followed by the male-biased treatment (25.31 ± 4.94), and lastly, the paired treatment (17.94 ± 4.90). For paired treatments, size matched mates’ body weights were correlated with the brood size in the clear water but not in the turbid water. In sex-biased treatments, fish’s weights best predicted the brood sizes when females were given a preference in mates. For sex-biased treatments, 75% of matings in clear water were size assortative, whereas mate preference was random in turbid treatments. Preliminary analyses (n=3) report greater levels of courtship behaviors for turbid treatments than clear treatments. On-going behavioral and statistical analyses will further elucidate the relationship between mate choice and reproductive success and will enable better predictions of reproductive patterns in the wild populations with varied sex-ratios. This study’s results highlight the critical need for interpreting the results of behavioral studies conducted in pristine lab conditions when investigating mating systems of coastal fishes adapted to eutrophic waters.

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