Spawning and early development of captive yellowfin tuna (Thunnus albacares)

In this study we describe the courtship and spawning behaviors of captive yellowfin tuna (Thunnus albacares), their spawning periodicity, the influence of physical and biological factors on spawning and hatching, and egg and early-larval development of this species at the Achotines Laboratory, Republic of Panama, during October 1996 through March 2000. Spawning occurred almost daily over extended periods and at water temperatures from 23.3° to 29.7°C. Water temperature appeared to be the main exogenous factor controlling the occurrence and timing of spawning. Courtship and spawning behaviors were ritualized and consistent among three groups of broodstock over 3.5 years. For any date, the time of day of spawning (range: 1330 to 2130 h) was predictable from mean daily water temperature, and 95% of hatching occurred the next day between 1500 and 1900 h. We estimated that females at first spawning averaged 1.6−2.0 years of age. Over short time periods (<1 month), spawning females increased their egg production from 30% to 234% in response to shortterm increases in daily food ration of 9% to 33%. Egg diameter, notochord length (NL) at hatching, NL at first feeding, and dry weights of these stages were estimated. Water temperature was significantly, inversely related to egg size, egg-stage duration, larval size at hatching, and yolksac larval duration

Ocean Futures for the World’s Largest Yellowfin Tuna Population Under the Combined Effects of Ocean Warming and Acidification

The impacts of climate change are expected to have profound effects on the fisheries of the Pacific Ocean, including its tuna fisheries, the largest globally. This study examined the combined effects of climate change on the yellowfin tuna population using the ecosystem model SEAPODYM. Yellowfin tuna fisheries in the Pacific contribute significantly to the economies and food security of Pacific Island Countries and Territories and Oceania. We use an ensemble of earth climate models to project yellowfin populations under a high greenhouse gas emissions (IPCC RCP8.5) scenario, which includes, the combined effects of a warming ocean, increasing acidification and changing ocean chemistry. Our results suggest that the acidification impact will be smaller in comparison to the ocean warming impact, even in the most extreme ensemble member scenario explored, but will have additional influences on yellowfin tuna population dynamics. An eastward shift in the distribution of yellowfin tuna was observed in the projections in the model ensemble in the absence of explicitly accounting for changes in acidification. The extent of this shift did not substantially differ when the three-acidification induced larval mortality scenarios were included in the ensemble; however, acidification was projected to weaken the magnitude of the increase in abundance in the eastern Pacific. Together with intensive fishing, these potential changes are likely to challenge the global fishing industry as well as the economies and food systems of many small Pacific Island Countries and Territories. The modelling framework applied in this study provides a tool for evaluating such effects and informing policy development

Genetic monitoring for spawning ecology of captive Yellowfin Tuna (Thunnus albacares) using mitochondrial DNA variation. Aquaculture 218:387–395

Abstract Mitochondrial DNA genotypes of captive broodstock of yellowfin tuna (Thunnus albacares) were compared with those of their offspring in order to monitor spawning frequency and periodicity. Among 38 broodstock individuals, 27 genotypes were observed, 18 of which established a single individual&apos;s identity. Spawned eggs and hatched larvae were collected on 48 sampling days over a period of 1 year. Among 538 eggs and larvae analyzed, 10 genotypes were observed; eight of them established a single female&apos;s identity, and two types were shared by two females. The spawning profiles of these females were determined by observing the occurrence of these genotypes in the offspring. Based on the dates when genotypes first occurred and on growth trajectories estimated for individual fish, the size of a female at first spawning was estimated to be 12 -28 kg and 75 -112 cm. Usually, multiple females spawned on a given date. The same genotypes were observed on almost any sampling day throughout the year. The results indicated that some individual females were capable of spawning almost daily for extended periods of time as long as they remained in the appropriate range of water temperatures and had sufficient food. Crown Copyright D 2003 Published by Elsevier Science B.V. All rights reserved

Improvement of Water Chemistry with Bacillus Probiotics Inclusion during Simulated Transport of Yellowfin Tuna Yolk Sac Larvae

The effects of adding a probiotic Bacillus spp. blend on shipping bag water quality and survival of yolk sac larvae of yellowfin tuna Thunnus albacares during a 24‐h mock shipment were investigated. To better detect effects on water quality, the trial was designed without the utilization of available chemical water quality or temperature modulators. Shipping water salinity (30.7–31.0‰) and temperature (24.0–26.7°C) reflected conditions utilized during larval rearing. Probiotic incorporation (15 mL/L, about 1.5 × 106 colony‐forming units/mL) resulted in significantly lower final concentrations of total ammonia nitrogen and un‐ionized ammonia in comparison with the control. Significantly higher final mean dissolved oxygen concentration observed in the probiotic treatment could have resulted from stress reduction. Although no statistical difference was detected in larval survival upon termination of the trial, improvements in water quality (reduced total ammonia nitrogen and increased dissolved oxygen) resulting from incorporation of Bacillus probiotics would yield added levels of safety during shipping and would reduce the chances of negative results while incurring minimal increases in shipping costs.Received January 28, 2010; accepted May 1, 201

キハダマグロの親魚用餌の産卵成績への影響および卵・仔魚への栄養素移行に関する研究

[Abstract]Successful spawning of yellowfin tuna, Thunnus albacares under land-based concrete tank facilities has been started almost two decades ago at the Achotines Laboratory of the Inter-American Tropical Tuna Commission (IATTC), Las Tablas, Los Santos, Panama. However, very little attempt has been made to study nutritional aspects of this valuable species. The quality of eggs and their offspring completely relies on quality of broodstock diet. ln addition, broodstock diet together with some environmental factors regulates the spawning performance, fecundity, hatching and larval performance. Two trials were conducted from May 22 -June 26 (Trial 1) and November 1 -December 13 (Tria12), 2011. Time to spawn, fertilized eggs, hatching rate and water parameters were collected on regular basis. Similarly, egg and oil globule diameter, length of newly hatched larvae (NHL) were measured and eggs and NHL were sampled for proximate analysis. The water quality parameters during the experimental period were fairly constant and may have no effect on spawning or hatching rate. The size of eggs was found very similar in both trials under the existing condition. The fecundity was found to have direct effect with the feed composition, and spawning was delayed by five minutes each day while the feed composition was in changing state in trial 1 (phase 1). The effect has c1early observed with low protein and lipid content in eggs and NHL in phase one. The results from this study indicated the delay of spawning might be due to low levels of lipid and protein transferred in eggs from diet. It seems that the prevailing environmental condition in Achotines laboratory is suitable for rearing broodstock; however, providing correct nutrition to the broodstock, the egg quality, spawning performance, hatching rate and larval performance could be improved in certain extent

Effects of elevated CO2 on metabolic rate and nitrogenous waste handling in the early life stages of yellowfin tuna (Thunnus albacares)

Ocean acidification is predicted to have a wide range of impacts on fish, but there has been little focus on broad-ranging pelagic fish species. Early life stages of fish are thought to be particularly susceptible to CO2 exposure, since acid-base regulatory faculties may not be fully developed. We obtained yellowfin tuna (Thunnus albacares) from a captive spawning broodstock population and exposed them to control or 1900 μatm CO2 through the first three days of development as embryos transitioned into yolk sac larvae. Metabolic rate, yolk sac depletion, and oil globule depletion were measured to assess overall energy usage. To determine if CO2 altered protein catabolism, tissue nitrogen content and nitrogenous waste excretion were quantified. CO2 exposure did not significantly impact embryonic metabolic rate, yolk sac depletion, or oil globule depletion, however, there was a significant decrease in metabolic rate at the latest measured yolk sac larval stage (36 h post fertilization). CO2-exposure led to a significant increase in nitrogenous waste excretion in larvae, but there were no differences in nitrogen tissue accumulation. Nitrogenous waste accumulated in embryos as they developed but decreased after hatch, coinciding with a large increase in nitrogenous waste excretion and increased metabolic rate in newly hatched larvae. Our results provide insight into how yellowfin tuna are impacted by increases in CO2 in early development, but more research with higher levels of replication is needed to better understand long-term impacts and acid-base regulatory mechanisms in this important pelagic fish.[Display omitted]•Little is known about how tuna species will respond to ocean acidification (OA).•CO2 altered nitrogenous waste excretion and metabolic rate in yolk sac larvae.•CO2 did not change yolk sac depletion in embryos.•CO2 did not alter nitrogen accumulation in yellowfin tuna.•Yellowfin tuna were more robust to CO2 than predicted

Seawater carbonate chemistry and metabolic rate and nitrogenous waste handling in the early life stages of yellowfin tuna (Thunnus albacares)

Ocean acidification is predicted to have a wide range of impacts on fish, but there has been little focus on broad-ranging pelagic fish species. Early life stages of fish are thought to be particularly susceptible to CO2 exposure, since acid-base regulatory faculties may not be fully developed. We obtained yellowfin tuna (Thunnus albacares) from a captive spawning broodstock population and exposed them to control or 1900 μatm CO2 through the first three days of development as embryos transitioned into yolk sac larvae. Metabolic rate, yolk sac depletion, and oil globule depletion were measured to assess overall energy usage. To determine if CO2 altered protein catabolism, tissue nitrogen content and nitrogenous waste excretion were quantified. CO2 exposure did not significantly impact embryonic metabolic rate, yolk sac depletion, or oil globule depletion, however, there was a significant decrease in metabolic rate at the latest measured yolk sac larval stage (36 h post fertilization). CO2-exposure led to a significant increase in nitrogenous waste excretion in larvae, but there were no differences in nitrogen tissue accumulation. Nitrogenous waste accumulated in embryos as they developed but decreased after hatch, coinciding with a large increase in nitrogenous waste excretion and increased metabolic rate in newly hatched larvae. Our results provide insight into how yellowfin tuna are impacted by increases in CO2 in early development, but more research with higher levels of replication is needed to better understand long-term impacts and acid-base regulatory mechanisms in this important pelagic fish

キハダ仔稚魚の栄養要求に関する研究 ―種苗生産用飼料開発への取り組み

[Abstract]Yellowfin tuna (YFT), Thunnus albacares is one of the most harvested fish around the world. Although successful spawning of this species has started almost two decades ago at the Achotines Laboratory of the Inter-American Tropical Tuna Commission (IATTC), Las Tablas, Los Santos, Panama, the nutritional requirements of this species are still unknown. Providing correct nutrition to the broodstock ensures the highest quality of eggs and fecundity, hatchability and high larval survival. While, development of a nutritionally balanced diet is a prerequisite for mass seedling production in hatchery condition which can easily switch from supply of expensive live prey including fish larvae as well, it is still far away of establishment for YFT juvenile. Therefore, this study was done to understand the basic nutritional requirements of this valuable species. Periodic sampling of broodstock diets including squid, sardine and commercial pellet, larval feed including rotifers, Artemia, newly hatched larvae and wild zooplankton (copepod, collected from adjacent sea) were done. The proximate and fatty acid composition of those samples revealed that the present larval feeding practice is suboptimal and unable to meet the maximum growth as compared with other scombroid. Restructuring of broodstock feeding is necessary with proper supplementation of docosahexaenoic acid (DHA). The water quality parameters during the experimental period were fairly constant and may have no effect on spawning or hatching rate. It was found that the minimum protein and lipid content under this experimental condition might be ca. 12.7 and 1.3%, respectively on wet weight basis. The preliminary information about the nutritional status obtained from this study will greatly help to develop nutritionally balanced diet for YFT, and further will ensure the mass production of seedlings in hatchery condition in near future