Research on tunas

• Early studies of black skipjack tuna

  In 1991, late-larval black skipjack tuna (Euthynnus lineatus) collected at sea were successfully reared to sexual maturity in the laboratory. This had not been accomplished previously for any species of tuna.
  
  From 1987 through 1994, larval and early juvenile black skipjack collected at sea were reared at the Laboratory. A series of experiments resulted in published studies of the nutrition, ageing and growth, endothermy and development of vision during larval and juvenile development of black skipjack.
  
  By 1996, with the expansion of the Laboratory facilities, research emphasis at Achotines shifted to the spawning and rearing of yellowfin tuna.

  

  Broodstock black skipjack tuna spawned in Laboratory tanks from 1991-1994

  

  Night-light caught postflexion larval and early-stage juvenile black skipjack

  

  Larval black skipjack tuna otolith with 9 daily increments used in ageing and growth studies

• Yellowfin broodstock: capture and transport

  Since early 1996, yellowfin have been caught in waters close to Achotines Bay, using rod and reel or hand lines, and transported to the Laboratory in tanks aboard skiffs. Prior to stocking in the laboratory tanks, the fish are measured, weighed, tagged with a microchip implant tag in the dorsal musculature, and injected with oxytetracycline (OTC). The tag allows each fish to be identified throughout its life in captivity, and injection with OTC establishes a temporal mark in the otoliths and vertebrae useful for studies of the growth of the fish.

  

  Hand lines and rod and reel are used to capture yellowfin tuna

  

  Yellowfin tuna caught at sea are lifted aboard for transfer to the Laboratory

  

  Yellowfin tuna are transferred from acclimation and grow-out tanks to the main broodstock tank after approximately 3 to 6 months in captivity

  

  Yellowfin grow to reproductive size and spawn in the main broodstock tank

  The 1300-m3 main tuna broodstock tank was designed to be large enough to reduce the stress of captivity and enhance the chances of yellowfin spawning

  Project(s):

  Project G.2.a
• Yellowfin broodstock: feeding and growth rates

  The broodstock yellowfin are fed a diet of squid, herring, and anchovy, supplemented with vitamins and minerals, at approximately 2.0 to 4.5% of their body weight per day.  Growth rates for 2 to 3-year-old yellowfin in the main broodstock tank have ranged from 0.02 to 0.10 kg/day and from 0.05 to 0.19 cm/day.

  

  Feeding yellowfin tuna in main broodstock tank

  

  Feeding yellowfin tuna in main broodstock tank

  Project(s):

  Project G.2.a
• Yellowfin spawning

  The initial group of 55 yellowfin tuna were stocked in the main broodstock tank in June and September of 1996 and began spawning by October of that year.  The yellowfin broodstock tank has been replenished with new fish periodically since 1999.  Spawning has occurred near daily in the main broodstock tank since inception.  To our knowledge, this represents the only long-term, successful spawning of yellowfin in land-based tanks anywhere in the world.  Spawning can be intermittent during February and March, when offshore upwelling, induced by northerly winds of the dry season, brings cooler water temperatures near shore and into the rearing tanks.  Spawning generally occurs from early afternoon to late evening.  The spawning events are usually preceded by several hours of courtship behavior (paired swimming, chasing). .

  The numbers of fertilized eggs collected after each spawning event in the main broodstock tank range from several hundred to several million. The eggs are collected by several methods, including siphoning and dipnetting at the surface and seining with a fine-mesh surface egg seine. Fertilized eggs are hatched in 300-liter cylindrical incubation tanks.

  

  Yellowfin tuna have spawned near daily in the main broodstock tank since 1996

  

  Cylindrical incubation tanks for the hatching of fertilized eggs

  

  Egg collecting net and basket in the main broodstock tank

  

  Egg collecting net and basket in the main broodstock tank

  

  Egg collecting net and basket in the main broodstock tank

  

  Fertilized yellowfin eggs during early morula

  

  Fertilized yellowfin eggs during embryonic stages of development

  Project(s):

  Project G.2.a

  Project E.5.b
• Studies of yellowfin eggs, larvae, and juveniles

  The larvae hatched from eggs spawned in captivity have been used in a variety of laboratory experiments to identify environmental or biological factors that are most important in controlling survival during the early life stages of yellowfin and other tunas.  A key goal of the IATTC ELH program is to understand and predict the factors that most strongly influence pre-recruit survival in tunas.  The ability to forecast yellowfin recruitment, prior to the age at entry to the fishery (6 months), would be a powerful stock assessment tool.
   
  Experiments have been carried out to examine the effects of larval and juvenile stocking densities, microturbulence, water temperature and dissolved oxygen, pH, light intensity, prey density, and prey selectivity on feeding incidence, survival, and growth of yellowfin larvae. Collaborative studies have also been conducted to examine the development of vision in larval and juvenile yellowfin.

  

  Yellowfin tuna larvae are studied in laboratory rearing experiments during the first week of feeding (4-day old; 3.5 mm in length)

  

  Temperature-and oxygen controlled tanks used for experiments with yellowfin larvae

  

  Temperature-and oxygen controlled tanks used for experiments with yellowfin larvae

  

  Micro acoustic Doppler current meter used in studies of the effects of microturbulence on the survival of yellowfin larvae. Inset figure shows a dome-shaped response of larval survival to increased microturbulence generated by aeration

  

  Size grading ocean collected zooplankton for prey selectivity studies

  Juveniles are routinely reared for 5-6 weeks after hatching, and have survived up to 158 days.  Growth in length and weight of larvae and early juveniles is rapid and non-linear.  Mean growth rates between 15 and 100 days of age are typically 1 to 3 mm/day.  The diet consists of enriched cultured plankton during the larval stages and early-stage juveniles are fed fish larvae until they can be transitioned to a minced fish or artificial diet (Video).

  
  Growth in length of yellowfin larvae between 2 and 25 days of age
   

  Project(s):

  Project N.2.a

  Project N.1.b

  Project G.3.a

  Project G.2.a

  Project G.1.a
• Genetic studies of yellowfin tuna

  In collaborative experiments with the National Research Institute of Far Seas Fisheries of Japan, tissue samples have been taken from broodstock yellowfin and their eggs and larvae to determine the amount of genetic variation in both adults and their offspring.  Novel genetic markers have been developed for yellowfin that provide the first direct evidence of Mendelian inheritance of nuclear DNA variants in a highly mobile, pelagic fish.  These markers have been used to analyze the spawning patterns of individual female yellowfin and to estimate the number of female fish contributing to individual spawning events.  Genetic studies of the broodstock, eggs, and larvae are ongoing with various collaborators from Kindai University, Japan and Macquarie University, NSW, Australia.

  
  DNA analytical laboratory

  

  Yellowfin eggs 14 hours after fertilization

  

  Yolk-sac larvae spawned in captivity can be linked genetically to spawning females

  Project(s):

  Project G.2.a

  Project E.5.b
• IATTC-University of Miami joint studies

  In November 2001, the IATTC entered into an agreement with the University of Miami’s Aquaculture Program and Center for Sustainable Fisheries to conduct joint studies of tunas and billfish at the Achotines Laboratory. The joint program resulted in investigations of aquaculture techniques used to rear yellowfin eggs and larvae with probiotics, extended photoperiods, and artificial feeds.  As part of this collaboration, an international workshop for scientists and students is conducted each year at the Achotines Laboratory to develop aquaculture techniques with yellowfin tuna.  Studies have also been conducted to test the feasibility of collecting, transporting and holding billfish broodstock at the Achotines Laboratory.
  Further collaboration will be conducted to study growth, nutrition and survival of pre-recruit life stages of tropical and subtropical tunas at the University of Miami and at the Achotines Laboratory.

  

  An international workshop for scientists and students is conducted each year at the Achotines Laboratory to develop aquaculture techniques with yellowfin tuna

  

  Collaborative studies on pre-recruit stages of tunas are being planned by UMAP and IATTC

  

  Live transport of sailfish to the laboratory shortly after capture

  Project(s):

  Project G.1.a

  Project N.2.a
• Comparative studies of yellowfin and Pacific bluefin tuna (Thunnus orientalis) larvae

  A joint Kindai University (KU)-IATTC-ARAP [Autoridad de los Recursos Acuáticos de Panamá] 5-year research project (from 2011-2016) was supported in Panama by the Japan International Cooperation Agency (JICA).  This project, which was conducted through the Science and Technology Research Partnership for Sustainable Development (SATREPS) program, involves comparative studies of the early life histories of Pacific bluefin and yellowfin tunas.  The research on Pacific bluefin, which is conducted at the Fisheries Laboratories of KU in Wakayama Prefecture, Japan, is being supported by the Japan Science and Technology Agency (JST).  The project officially ended in March 2016 but continuity studies by KU and IATTC of the comparative experimental work with bluefin and yellowfin larvae are being continued.  
  
  
  Major accomplishments of the project have included comparative studies of the survival and growth potential of both species during the first two weeks of feeding, a comparison of starvation resistance at first feeding, and a description of the feeding dynamics and prey selectivity of both species of larvae.  Additionally, juvenile yellowfin were successfully reared at Achotines, transferred to an offshore sea cage, and transferred back to larger land-based tanks.  Some of these fish grew to near-recruitment sizes of 25 to 28 cm and survived up to 158 days.  The results from these experiments will be incorporated into the development of recruitment prediction models for Pacific bluefin and yellowfin to aid in the management of these stocks.

  

  Fertilized Pacific bluefin eggs at Kindai University’s Fisheries Laboratory in Japan

  

  6-day old feeding larvae at Kindai University’s Fisheries Laboratory in Japan

  

  Fertilized yellowfin eggs at the IATTC’s Achotines Laboratory in Panama

  

  6-day old feeding larva at the IATTC’s Achotines Laboratory in Panama

  

  Yellowfin tuna larvae were reared from fertilized eggs in land-based tanks

  

  The juveniles were transferred to an offshore sea cage

  

  After 2.5 months of age, the juveniles were transferred back to land-based tanks at the Achotines Laboratory

  

  Juveniles were reared for several additional months in the land based tank where they were fed chopped fish and squid. The oldest individual grew to 28 cm in length and was 158 days old when it died

  Project(s):

  Project G.2.a

  Project G.1.a
• Collaborative studies on the effects of ocean acidification and stage-specific modes of respiration and osmoregulation during Early development of yellowfin tuna

  Increasing ocean acidification is a concern for its potential effects on the growth, development, and survival of early life stages of tunas in oceanic habitats and on the spatial extent of suitable nursery habitat for tunas. To investigate the potential effects of ocean acidification on yellowfin early life stages, a laboratory study was conducted at the Achotines Laboratory in 2011 with multiple collaborating scientists from the Secretariat of the Pacific Community, Macquarie University (NSW, Australia), University of Gothenburg (Sweden), Max Planck Institute of Meteorology (Germany), Collecte Localisation Satellites (France), and the University of California at Santa Barbara.  The study results indicated the potential for significantly reduced survival, condition, and size of larvae and prolonged egg hatch times at acidification levels that are similar to near future predicted levels.  Histological analysis of organ development in larvae indicated significant organ damage at pH levels higher than those at which significant impacts were detected on survival and growth. Analysis is also being conducted on larvae sampled from the 2011 experiments to describe the effects of ocean acidification on the morphology of otoliths of yellowfin larvae.
   A collaborative investigation was also initiated with Scripps Institution of Oceanography and the U.S. National Marine Fisheries Service to study the development of larval yellowfin capacity for osmoregulation in relation to gas exchange by immunolabeling and mapping the distribution of ionocytes (also known as mitochondrial rich cells or chloride cells) and examining the gill morphology from a developmental series of larvae.  Having an understanding of stage-specific modes of respiration and osmoregulation should provide a basis for understanding larval susceptibility to naturally occurring environmental stressors such as hypoxia and changes in water salinity.

  

  Eggs & larvae exposed to one of four target ph (CO2) treatments in replicate tanks until 9 days of age

  

  Gas flow controllers & mixing manifold to deliver desired CO2 level to replicate treatment tanks

  

  Baskets used during the egg stage and batched larvae were release into the tank

  

  CO2 tanks and air compressor

  

  Abnormal development of a 7 day old larval yellowfin from pH treatment 7.3 showing vertebral fusion and renal calcifications (i.e. kidney stones)

  

  Histological sections of healthy and degrading organ tissues with decreasing pH (increasing pCO2)

  
  Stained cutaneous and gill filament ionocytes (AKA mitochondrial-rich cells or chloride cells) in an 11 day old yellowfin larva (5.2 mm in length).

  Project(s):

  Project N.2.a
• Nutritional studies

  Dietary composition and nutritional requirements of yellowfin larvae and juveniles were analyzed and studied under the collaborative SATREPS project. Proximate composition (moisture content, fat, crude protein, ash and carbohydrates) and protein analyses were performed on larvae, juveniles, their zooplankton prey, and prey enrichment media.
  
  Dr. Alejandro Buentello, (Texas A&M University adjunct professor and Fish Nutritionist and Physiologist with Ichthus, Inc.) and Dr. Juan Sierra (University of Miami) are studying the nutritional composition of various prepared diets and their effect on palatability and growth of 45-65 cm FL yellowfin tuna.  Dr. Buentello had previously collaborated with the IATTC’s Early Life History group on a study of digestive enzyme activities and amino acid composition of early juvenile yellowfin tuna which resulted in a publication in the journal Aquaculture.
   

  

  Nutritional analysis in the laboratory

  

  Nutritional analysis in the laboratory

  
      Studies on the nutritional composition of various prepared diets and their effect on palatability and growth of 45-65 cm FL yellowfin tuna

  Project(s):

  Project G.1.a
• Tuna bycatch reduction technology studies

  Tuna bycatch-reduction devices have been tested at the Achotines Laboratory to reduce the catch of non-targeted species of fish and smaller sizes of tunas in the purse seine and FAD (fish aggregating devices) fisheries.  Different types of sorting grids and bubble curtains have been tank tested by the IATTC bycatch program to allow smaller fish to escape while retaining larger fish.  
  
  In a research project funded by the International Seafood Sustainability Foundation (ISSF), Dr. Gala Moreno of ISSF and Dr. Guillermo Boyra and Xiker Salaberria of AZTI-Tecnalia, Spain, measured the acoustic properties (species-specific target strength related to length and behavior and species-specific-frequency response) of 45 to 71 cm yellowfin in the juvenile sea cage near the Achotines Laboratory for use as a possible bycatch mitigation measure for the drifting FAD fishery.  The size class of 40-60 cm yellowfin is often associated with skipjack and bigeye tunas around drifting FADs.  Each species has distinct acoustic properties which can be detected remotely by echo-sounder buoys so that areas of high presence of undesired sizes and tuna species at FADs could be avoided with development of this technology.
  
  The IATTC bycatch research program also conducted a feasibility study at the Achotines Laboratory with funding by the European Union, to design and deploy three anchored prototype FADs that were non-entangling and biodegradable.  The FADs survived for up to 5 weeks offshore from the Laboratory.  The design will be modified further to withstand strong ocean conditions for up to 4 months before being deployed in fishing areas.

  

  Two different sorting grids tested in a tank at Achotines. Red arrow indicates a yellowfin tuna swimming through the grid

  

  A small group of 45-71 cm yellowfin tuna was stocked in the off-shore sea cage near the laboratory where acoustic measurements were collected from echo-sounder buoys at the surface of the sea cage

  
  Radiograph of a yellowfin tuna swim bladder. Acoustic target strength and frequency response correspond to the proportion of swim bladder size relative to fish size

  

  Photograph of one type of biodegradable and non-entangling FAD deployed offshore of Achotines

  

  Schematic of one type of biodegradable and non-entangling FAD deployed offshore of Achotines

  Project(s):

  Project M.1.c
• Research on snappers and corvinas

  A scientist from the Autoridad de los Recursos Acuáticos de Panamá (ARAP) , working with Laboratory staff and visiting Japanese scientists, established spawning broodstock populations of polla drum (Umbrina xanti), a species of corvina, and spotted rose snappers (Lutjanus guttatus) in 1996 and 1997.  This represents the first successful spawning in captivity for both of these species.
  
  The snapper broodstock have been spawning naturally since 1997 and the full life cycle has been completed. The broodstock population was rebuilt  in recent years.  During April-June 2013, a major fishing effort was conducted, and more than 100 spotted rose snappers were collected in local waters.  At the end of January 2017, 15 fish continued to be held in the broodstock snapper tank.  These fish began spawning during 2015 and continue to spawn intermittently.

Collaborative research

The IATTC’s Early Life History Research Group   maintains close affiliations with universities, government agencies, and private research organizations and institutions at local, national, and international levels. The Achotines Laboratory serves as a unique site for conducting the collaborative research.

Project Collaborations with the IATTC ELH Group	Affiliations
The effects of ocean acidification during early development of yellowfin tuna	Secretariat of the Pacific Community; Macquarie University, NSW; Australia; University of Gothenburg, Sweden; Max Planck Institute of Meterorology, Germany; Collecte Localisation Satellites, France; University of California at Santa Barbara
Comparative studies of growth and survival of yellowfin and Pacific bluefin larvae	Kindai University, Japan; Panama Aquatic Resources (ARAP); Japan International Cooperation Agency; Japan Science and Technology Agency
Growth, nutrition, and survival of pre-recruit life stages of tropical and subtropical tunas	University of Miami
Stage-specific modes of respiration and osmoregulation of yellowfin tuna larvae	Southwest Fisheries Science Center, NMFS; Scripps Institution of Oceanography
Development of yellowfin and snapper broodstock	Overseas Fishery Cooperative Foundation, Japan; ARAP; Japan Sea-Farming Association; Monterey Bay Aquarium, CA
Nutritional studies of prepared diets for 1-2 year old yellowfin tuna	Texas A&M University; Ichthus, Inc.; University of Miami
Digestive enzyme activities and amino acid composition of early juvenile yellowfin tuna	Texas A&M University
Mitochondrial DNA analysis of yellowfin tuna larvae collected in the Panama Bight	National Institute of Far Seas Fisheries, Japan; National Research Institute of Fisheries Science, Japan
Microturbulence in the feeding environment of yellowfin tuna larvae	University of Tokyo Nagasaki University
Developmental changes in the visual pigments of yellowfin tuna	Cornell University, NY; University of Washington
Development of acoustic techniques to identify tuna species at fish aggregating devices (FADs) in order to mitigate bycatch in the tuna fishery	International Seafood Sustainability Foundation; AZTI Tecnalia, Spain
Development of non-entangling and biodegradable FADs for the tuna fishery	IATTC Bycatch Research Program; European Union
Size-specific regional endothermy, swimming performance, and respirometry in black skipjack tunas	California State University, Fullerton
Genomics and reproductive biology of black skipjack tuna	Tokyo University of Marine Science and Technology
Mitochondrial DNA variation and the genetic monitoring for the spawning ecology of captive yellowfin tuna	INTEM Consulting Inc., Japan; Overseas Fishery Cooperative Foundation, Japan; National Institute of Far Seas Fisheries, Japan
Mendelian inheritance and variation of microsatellite DNA markers in yellowfin tuna	Ehime University, Japan; National Institute of Far Seas Fisheries, Japan; Metocean Environmental, Inc. Japan; Overseas Fishery Cooperative Foundation, Japan; Tohoku University, Japan
Direct evidence for Mendelian inheritance from a single pair of yellowfin tuna parents and their offspring	National Institute of Far Seas Fisheries, Japan; Overseas Fishery Cooperative Foundation, Japan; Japan Gene Research
Marine fish assemblages associated with Fish Aggregating Devices (FADS)	Northern Arizona University
Cryopreservation of yellowfin tuna embryos	Cryoocyte, Inc., MA, USA
Use of light traps to determine abundance of early-juvenile tunas	Australian Institute of Marine Science
Mitochondrial DNA analyses of tuna larvae collected in the Panama Bight	National Research Institute of Fisheries Science Nagai, Japan; National Research Institute of Far Seas Fisheries, Japan
Shipments of yellowfin eggs and larvae to the United States	Hubbs Sea World Research Institute; University of Maryland
A survey of fishes occurring in nearshore waters of the Azuero Peninsula of Panama	National Marine Fisheries Service Systematics Laboratory

Independent Projects	Affiliations
Restoration and regeneration of dry, tropical rain forest	Smithsonian Tropical Research Institute, Panama; Yale University/ Environmental Leadership Training Initiative (ELTI)
Trophic and behavioral ecology of land hermit crabs	University of Michigan