An Intensive, Large-Scale Batch Culture System to Produce the Calanoid Copepod, \u3ci\u3eAcartia tonsa\u3c/i\u3e

A major obstacle to the development of hatchery production for juveniles of many marine species is the difficulty in successfully feeding early larvae. Copepods contribute to the natural diet of most marine fish larvae and feature characteristics ideal for early larval feeds including small size and suitable nutrient content. However, the use of copepods as larval feeds is limited by the inability to consistently produce them in sufficient quantities to support large-scale fish culture. Here, an innovative design for an intensive, indoor batch culture system to produce the calanoid copepod Acartia tonsa (Dana 1849), a prime candidate for use as a live food item, is described. The system features integrated grow-out and egg-production units that can be operated sequentially by 2.5 full-time employees to produce a predictable daily output of nauplii for use as live feed. The system output was on average 22 million eggs d−1 (21,955,420 ± 8,709,668) with an average hatch rate of 49% (49.1 ± 14.8) over three seasons

A Histological Study of Gametogenesis In Captive Red Snapper \u3ci\u3eLutjanus campechanus\u3c/i\u3e

Gametogenesis was monitored histologically in wild-caught red snapper (Lutjanus campechanus, Poey) maintained in captivity under simulated natural photothermal conditions. Gonads were collected every 2–3 weeks (average n = 14) for histology during the pre-spawning season (February to May, temperature increasing from 16°C to 24°C). Primary vitellogenic oocytes were first observed in one female when temperature reached 20°C. Subsequent samples revealed females in pre-vitellogenesis or at early stages of vitellogenesis, although one female had tertiary vitellogenic (Vtg3) oocytes. The first histological signs of spermatogenesis were observed when temperature reached 17°C. Spermatozoa were observed in testicular lobules of all males sampled on 14 May (24°C) but little or no sperm was released during manual stripping. Ten males and 10 females were left in tanks and monitored for spawning. No egg release was observed during the monitoring period that encompassed the natural spawning season of wild red snapper. Ovarian biopsies taken during the late spawning season (16 July) revealed that four of eight sampled females had Vtg3 oocytes. Males were manually stripped but released no sperm. These results indicate that captive red snapper can complete gametogenesis in photothermal controlled systems. Additional research is needed to develop procedures that will achieve reliable maturation and spawning