Seahorses Hippocampus sp. are fishes with unique morphological and ecological characteristics that make them particularly susceptible to overfishing, bycatch and anthropogenic disturbances. The seahorse trade worldwide has been increasing in recent years and aquaculture has been proposed as an alternative to address unsustainable trade of seahorses for traditional medicine and ornamental industry. However, the lack of basic information regarding growth patterns and developmental stages hinders the a dvances in stablishing the optimal culture conditions.
The Pacific seahorse Hippocampus ingens is the sole species on Hippocampus found in the Pacific coast, with a range extending from California to southern Peru. It is most commonly associated with algae or rocks, and strongly associated with soft corals and coral reefs . In the present stud y we report the growth and development of juvenile H. ingens kept under culture conditions during the first 30 days of development.
Pacific seahorse juveniles were obtained from one spawn of H. ingens broodstock held under culture conditions in the commercial farm INGENS Cultivos Marinos in Mazatlán, Mexico. Juveniles were maintained in 50L plastic tanks. Seawater was treated with mechanical (5μm), biological and UV filtration. Culture conditions in the aquaria were maintained at a temperature of 24-27ºC, salinity of 33-35 ups, gentle aeration, a 12:12 photoperiod and O2 saturation of 100%. Juveniles were fed with Artemia nauplii, prey density fluctuated from 5-10 nauplii/ml.
Every day, starting with the newly born juveniles (day 1) and until day 30, three juveniles were sampled, anesthetized with a 4% phenoxyethanol solution, weighted at the nearest 0.0001g and photographed with a digital camera. Standard length was calculated in every photograph using an image analysis software. Weight gain (WG), specific growth rate (SGR) and condition factor (CF) during the studied period were estimated as follows WG(%)=(Wf−Wi)/Wi×100; SGR(%)=((lnWf−lnWi)/t)×100; CF=(W/L)×100 where, Wf is the final weight (g),W is the weight (g),Wi is the initial weight (g), SL is the standard length (cm), and t is the duration (d).
Newly born juveniles showed an initial SL of 7.502 ± 0.121 ( average ± std dev) mm and an average weight of 0.0010 ± 0.0001g. In the end of the study at day 30, the maximum SL was 32.658 ± 3.58 mm and an average weight of 0.0723 ± 0.0254g. Our results suggest the presence of two developmental stages, the first one during the first 14 days with a low SGR , WG and CF and the second during the last 16 days with a significant increase of these parameters. The specific growth rate during the period studied was 0.15 gr/day.