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ANALYZING DWARF SEASHORSE (HIPPOCAMPUS ZOSTERAE) REPRODUCTIVE PARAMETERS THROUGH JUVENILE GROWTH AND SURVIVORSHIP RATES**

Abstract

The dwarf seahorse, Hippocampus zosterae, is a flagship species whose population dynamics and reproductive patterns can provide insight on the health of threatened seagrass ecosystems. This study aims to better understand dwarf seahorse reproductive parameters, including brood sizes, juvenile growth, and survivorship rates. During the summers of 2021 and 2022, seahorses collected from Tampa Bay were brought into the lab for mating trials. To evaluate effects of animal measuring techniques on growth and survivorship, offspring from those trials were divided into three equal treatments: the photo treatment where offspring were photographed for body length, the weight treatment where offspring were weighed for mass, and the non-treatment group where offspring were not handled or measured. Offspring in the photo and weight treatments were measured every eight days. Ongoing measurements of photographs using ImageJ will determine body lengths. Lengths from the photo treatment and masses from the weight treatment will be used to calculate growth curves. To determine survivorship rates, offspring in each treatment were counted every four days. Brood sizes ranged from 8 to 70 offspring, averaging 31.7 ± 3.4 offspring per brood (n=25). Average paternal mass was 196.5 ± 12.6 mg (n=25) after giving birth, while average offspring mass was 2.07 ± 0.045 mg across all broods at birth (n=25 broods, 243 offspring). Trends show relatively high survivorship within the first 30 days after birth, followed by a decline. Preliminary results suggest there is no difference between treatments, resulting in a 20% survival in all treatments by day 100. These results follow similar trends found in other seahorse species, including those with larger reproductive outputs than the dwarf seahorse. These outcomes contribute to our knowledge of seahorse life history traits, providing valuable information for recruitment and survival patterns of smaller species to ultimately enhance seahorse conservation practices in the wild.

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