Tagged tuna graphic by Nancy Hulbirt, SOEST Illustration.

PFRP Biology Projects

Early Life Stage Dispersal of Yellowfin Tuna (Thunnus albacares) in the Central North Pacific

Progress Reports: FY 2012, FY 2011

Project Background and Justification

The purpose of this project is to understand larval dispersal patterns of yellowfin tuna (Thunnus albacares) in the Hawaiian Region. Specifically, we will quantify the degree of mixing between different Pacific stocks due to larval transport and export, and how these patterns change within different scenarios: El Niño, La Niña, size and location of breeding stocks. We will also determine the probability density functions (PDFs) of larval distributions under these different scenarios, with a view that such information can be incorporated into stock assessment and prediction models. We will also examine how flow characteristics, specially the presence of persistent transport barriers in the flow, influence the distribution of larvae.

Yellowfin tuna is one of the most important commercially harvested tuna species in the Pacific, and represents a large percentage of Hawaiian longline, handline, and troll fisheries (WPRFMC 2009). In order to adequately manage these fisheries it is imperative to understand the species movement patterns throughout its life history (Palumbi 2004). Previous research contradicted the status quo that all tuna species are highly migratory (Sibert and Hampton 2003, Schaefer et al. 2007, D. Wells and J. Rooker, pers. comm.). Information achieved from tagging studies has revealed that yellowfin tuna are characterized by restricted movement around the Hawaiian Islands, seamounts and FADS (Itano and Holland 2000, Sibert and Hampton 2003, Dagorn et al. 2007). Moreover, analyses of otolith chemical and stable isotope signatures concluded that the one year old yellowfin sub-adults caught in the Hawaiian inshore fisheries are locally spawned (D. Wells and J. Rooker, pers. comm.). However, questions regarding the origin of the tuna fished and the degree of stock mixing due to tuna movement at different life stages still remain unanswered. By understanding the connectivity patterns and describing how circulation influences the distribution of fish larvae, the proposed research is a step towards correcting this lacuna.

We will investigate the early life stage movement of yellowfin tuna, quantifying the degree of larval self-retention in the Hawaiian region and export to or from other tropical regions of the Pacific, thus providing supplemental information on the origin of yellowfin tuna available to Hawaii fisheries that is vital for local-scale management. The objectives of this project are linked to the research priorities of the PFRP listed in the 2005 Research Priorities Workshop Report to support management decisions at both regional and Pacific scales, and closely related to section 5 Ecosystem Integration (examine movement to define functional sizes of ecosystem units). This research will establish the relationship between spawning areas, larval transport pathways and the presence of oceanographic features, specially mesoscale structures and persistent transport barriers, which again relates to the research priorities of Ecosystem Integration (influence of mesoscale oceanography on ecosystems) and Biology and Life History (investigation of early life history of tuna particularly related to the development of marine protected areas as a management tool).

We will accomplish this by incorporating the output from a three-dimensional model that simulates ocean circulation (HYCOM) into a biological model (BOLTS) that depicts adult spawning strategies, larval development, behavior, and dispersal (Paris et al. 2007). This allows the characterization of larval dispersal pathways in the Hawaiian archipelago and we will investigate how these patterns vary across years and over ecological time scales relevant to the management of pelagic resources. In summary, this project fills a gap in the understanding of marine population dynamics in the study area, while having the potential to improve stock assessment and fisheries management.

Objectives and Hypotheses

The goal of this project is twofold: i) to gain scientific knowledge about population connectivity by early life stage dispersion in the Hawaiian region and ii) to determine the impact of the flow on larval dispersion characteristics around Hawaii. The hypotheses that will be addressed in this project are:

Methodology

The velocity fields used in this study are outputs from global and regional implementations of a hydrodynamic model, the HYbrid Coordinate Ocean Model (HYCOM). The adult spawning strategy, larval development, behavior, mortality and settlement will be depicted by the BiOphysical Larval Tracking System (BOLTS, Paris et al. 2007). Analyses of the flow will identify the main physical features that play an important role in larval transport, such as eddies and transport barriers.

Expected Outcomes

Broader Impacts

The results obtained from this proposed research will have a broad range of applications aside from improving our scientific knowledge of larval dispersal. The modeling experiments can be used to define efficient larvae sampling strategies in order to better understand yellowfin tuna early life stage movements around the Hawaiian Islands. The establishment of efficient management measures to protect yellowfin tuna fishing stocks will be enhanced by the identification of sources and sink locations, and of areas contributing to replenish yellowfin tuna fisheries populations (i.e., areas that release larvae that will be retained). Ultimately, the results can be adapted and applied to other locations and species, promoting and supporting marine conservation efforts. The results will be communicated by presentations at scientific meetings, and by the publication of at least three scientific papers. More importantly, the results will be communicated to managers and policy makers, by both informal and formal meetings and through the preparation of a report incorporating the major findings of this research.

Funding for this project to be available late 2010.

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References

Dagorn L, Holland KN, Itano DG (2007) Behavior of yellowfin (Thunnus albacares) and bigeye (T. obesus) tuna in a network of fish aggregating devices (FADs). Marine Biology DOI 10.1007/s00227- 006-0511-1.

Itano DG, Holland KN (2000) Movement and vulnerability of bigeye (Thunnus obesus) and yellowfin tuna (Thunnus albacares) in relation to FADs and natural aggregation points. Aquatic Living Resources, 13:213-223.

Palumbi, S (2004) Marine reserves and ocean neighborhoods: The Spatial Scale of Marine Populations and Their Management. Annual Review Environment and Resources, 29:31–68.

Paris CB, Cherubin, LM, Cowen, RK (2007) Surfing, spinning, or diving from reef to reef: effects on population connectivity. Marine Ecology Progress Series, 347:285-300.

Schaefer KM, Fuller DW, Block BA (2007) Movements, behavior, and habitat utilization of yellowfin tuna (Thunnus albacares) in the northeastern Pacific Ocean, ascertained through archival tag data. Marine Biology, 152:503–525.

Sibert J, Hampton J (2003) Mobility of tropical tunas and the implications for fisheries management. Marine Policy, 27:87-95.

WPFMC (2009) Pelagic Fisheries of the Western Pacific Region: 2008 Annual Report. Prepared by the Pelagics Plan Team and WPRFMC staff, Western Pacific Regional Fishery Management Council, Honolulu, Hawaii.

Principal Investigators

Dr. Kelvin Richards
International Pacific Research Center
University of Hawaii
SOEST
1680 East-West Road, POST 401
Honolulu, Hawaii 96822
USA
Phone (808) 956-5399
FAX (808) 956-9425
email: rkelvin@hawaii.edu

Dr. Claire Paris-Limouzy
Rosenstiel School of Marine & Atmospheric Science
University of Miami
4600 Rickenbacker Causeway
Miami, FL 33149 USA
Phone (305) 421-4219
FAX (305) 421-4600
email: cparis@rsmas@miami.edu

Collaborators:
Dr. Jay Rooker, Texas A&M
email: rookerj@tamug.edu
Mr. David Itano, UH, JIMAR, PFRP
email: dgi@hawaii.edu

 

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