Hatchery methods and natural, hormone-implant-induced, and synchronized spawning of captive Atlantic croaker (Micropogonias undulatus) Linnaeus 1766
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The Atlantic croaker Micropogonias undulatus Linnaeus 1766 is a candidate for multiple purpose aquaculture production including use as a baitfish and foodfish. Controlled production of Atlantic croaker could alleviate seasonal availability, establish a steady supply, provide size-specific grades of bait, alleviate pressure on wild stocks, diversify aquaculture businesses, and contribute to foodfish sales. To achieve these potential benefits, development of commercial-scale spawning protocols must occur. Therefore, a study was conducted to determine: 1) if Atlantic croaker could be passively spawned in a captive environment; 2) if hormone implants could be used to actively spawn Atlantic croaker or improve fecundity; 3) if environmental control and hormone implants could be used to synchronize spawning of Atlantic croaker. Wild broodfish (mean SE; 329 11. g; 28.7 0.3. cm TL) were captured from Trinity Bay, Texas, pellet trained, and held under controlled photoperiod and temperature conditions. The treatments used were: 1) natural spawning (no hormone treatments); 2) pre-optimal temperature hormone implant (implant injected at 25C; 75g salmon gonadotropin-releasing hormone analogue; sGnRHa); 3) optimal temperature hormone implant (implant injected at 23C; 75g sGnRHa); or 4) post-optimal temperature hormone implant (implant injected at 21C; 75g sGnRHa). The total production from all treatments (N=36 females; 24 males) included 30 total spawning events during the 120. day study, which yielded 2,922,510 eggs (3064. mL eggs). The mean water temperature and photoperiod at time of spawning were 19.9C and 10.1 h of daylight, respectively. The post-optimal implant treatment resulted in a greater number of spawning events per tank (5.0 0.0), the shortest period of latency (3 0 days), larger volume of eggs spawning event (170 40. mL), greater quantity of eggs spawning event (160,203 37,943), and greater fertilization rate (51.9 5.6%) than the other hormone implant treatments. The fish allowed to spawn naturally or in the post-optimal treatment often produced similar results, but fish in the post-optimal treatment produced more spawns per tank (5.0 0.0 compared to 1.7 0.3), had greater fecundity (267,004 33,191 eggs female compared to 49,090 22,061 eggs female), and spawning was highly synchronized (5. days compared to 33. days). The results of this study demonstrate that Atlantic croaker can be spawned passively in a captive environment, but hormone implants used to actively induce spawning can improve fecundity and synchronize spawning for commercial production. 2010 Elsevier B.V.
