Determining Aquaculture Bottlenecks of Pacific Threadfin: Year 1 Final

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Determining aquaculture bottlenecks of Pacific threadfin (Polydactylus sexfilis): Increasing fry survival, growth, and quality 2011 CTSA Progress Report to the Public :

Determining aquaculture bottlenecks of Pacific threadfin ( Polydactylus sexfilis ): Increasing fry survival, growth, and quality 2011 CTSA Progress Report to the Public Charles W. Laidley Finfish Department, Oceanic Institute Waimanalo, Hawaii

Background:

Background Long-term investment in Pacific threadfin ( moi ) culture R&D has helped create hatchery technologies leading to the development of commercial moi production operations in Hawaii Hawaii served as the test-site for the Hawaii Offshore Aquaculture Research Project (HOARP), leading to the initiation commercial open ocean cage operations in the U.S. Current operations are generating approximately 1 million moi fingerlings per year for commercial production using the Sea Station submersible cage design In order to achieve full economic viability, it is necessary to further scale-up hatchery and open ocean growout operations

Egg supply:

Egg supply Moi broodstock readily spawn in land-based broodstock tank systems Under captive conditions broodstock spawn through out the year, although egg output varies with season despite relatively constant water temperatures (26° to 27°C) Moi spawn 3 to 5 days each lunar cycle, peaking at 8 to 10 days after each full moon Hatchery egg supplies are generally limited by winter (off-season) spawning output levels Broodstock take 4 to 5 years to mature through male to high-quality egg-producing females

Broodstock Health:

Broodstock Health Over the years we are seeing increased frequency of broodstock mortality associated with appearance of thyroid hyperplasia (i.e., goiters) Goiters develop slowly over years, peaking in occurrence from 3 to 5 years in captivity Goiters appear to affect both males and females relatively equally The loss of prime broodstock has significant affects on egg supplies

Thyroid Hyperplasia in Moi Broodstock:

Thyroid Hyperplasia in Moi Broodstock Thyroid gland produces key metabolic hormones thyroxine (T4) and triiodothyronine (T3) Iodine is a key chemical constituent of the thyroid hormones. Iodine insufficiency limits fishes ability to produce T4 and T3 Thyroid hormones (T3 & T4) play critical roles in a multitude of cellular functions including gametogenesis and early development Under iodine insufficiency, negative feedback loops from brain and pituitary hyper-stimulate the thyroid gland in effort to restore thyroid hormone levels The “over-stimulated” gland grows extremely large leading to physiological and anatomical impairment of normal function ... and eventually fish mortality

Objectives:

Objectives 1. To assess the capacity to increase thyroid hormone deposition into fertilized moi eggs through dietary and/or rearing water iodine supplementation. 2. To assess the efficacy of increased TH deposition in moi eggs to improve the survival and growth of moi larvae and fry to stocking size. 3. To determine the efficacy of adding iodide to larval/fry rearing water to increase their survival, and growth to stocking size. 4. To prepare reports, and publications for dissemination and transfer of technology and methodologies to the public.

Objective 1: To assess the capacity to increase thyroid hormone deposition into moi eggs through dietary and water iodine supplementation:

Objective 1: To assess the capacity to increase thyroid hormone deposition into moi eggs through dietary and water iodine supplementation Experimental Procedure: Moi broodstock from earlier studies were used to examine the effects of iodine supplementation through either the water supply or diet on goiter related mortality rates, reproductive performance, and egg thyroid hormone content Results: Anuenue broodstock had much higher egg thyroid hormone levels than broodstock maintained in low iodine OI/SLP well water Iodine supplementation through the water supply (raw + KI) and through several diets ( Vitalis and OI diet) helped reduce goiter related mortalities and significantly increased egg thyroid hormone content However the treatments also yielded lower egg production rates As broodstock are used in fingerling production, all fish were returned to the raw smelt/squid/shrimp diet. Note: Thyroid hormone assays were completed by Dr. Grau’s team at the Hawaii Institute of Marine Biology as part of thesis work of Eli Witt (2009)

Objective 1 Continued::

Objective 1 Continued: Both routes of iodine supplementation (water and diet) appear effective in reducing goiter development and improving the thyroid status of broodstock. The dietary route is both more cost effective and substantially easier to conduct However … dietary requirements for broodstock egg production are best met using the raw smelt/squid/shrimp diet Therefore … under year two project activities we will test a modified dietary supplementation approach which uses the high nutrition raw (smelt/squid/shrimp) dietary components are ground and stuffed with vitamin and iodine supplementation into sausage casings Results to date: Diet transition (Sept/Oct 2010) to the sausage diet resulted in a temporary reduction in feed intake relative to the control raw diet fed group. Fish now feed quite strongly on the supplemented diet with slowly increasing feed rates, while the control diet group less vigorously, with feed rates gradually declining Although the spawning performance of the supplemented diet group declined during diet transition, they are now substantially outperforming the untreated (raw) group. We are collecting all spawned eggs for analysis of egg thyroid hormone level and will test eggs from each treatment group for hatchery performance toward the end of year two project activities

Objective 2: To assess the efficacy of increased thyroid hormone deposition in moi eggs to improve hatchery performance:

Eggs from 3 broodstock treatment groups were tested for effects on larval growth and survival: Raw – alternating feedings of raw smelt, squid and shrimp KI – same diet as raw treatment with iodide supplementation of the water Goiter - fish with large goiters that were removed from the raw treatment group Somewhat surprisingly … neither low thyroid hormone levels in eggs nor iodine supplementation appeared to have any effects (positive or negative) on hatchery performance. This trial will be repeated in year two with eggs from control (raw diet) and a vitamin and iodine-supplemented sausage diet Objective 2: To assess the efficacy of increased thyroid hormone deposition in moi eggs to improve hatchery performance

Objective 3: Efficacy of adding iodide to larval/fry rearing water to increase their survival, and growth to stocking size:

Objective 3: Efficacy of adding iodide to larval/fry rearing water to increase their survival, and growth to stocking size E arlier work conducted in collaboration with Dr. Grau’s team at HIMB (Witt et al. 2009) found improved growth and survival of larvae reared in ocean water compared with the low-iodine well water Recent moi hatchery runs revealed even more striking differences in hatchery performance when larvae are reared in ocean water compared with those reared in low-iodine well water Project activities under year two of the project will specifically examine hatchery performance of moi larvae with, and without supplementation of iodine in the larval rearing water supply

Objective 4: To prepare reports, and publications for dissemination and transfer of technology and methodologies to the public. :

Objective 4: To prepare reports, and publications for dissemination and transfer of technology and methodologies to the public. Published manuscript by Eli Witt et al. on the correlation between environmental iodide and larval growth, performance, and whole body concentrations of thyroid hormone and cortisol in Pacific threadfin. Aquaculture (2009) 289:357-364. Current broodstock and larval rearing research efforts will be disseminated through presentation and peer-review publication upon completion of trials

Special thanks to …:

Special thanks to … Center for Tropical & Subtropical Aquaculture National Oceanic & Atmospheric Association US Dept. of Agriculture

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