Defining the Habitat of Pacific Tuna of the Eastern Tropical Pacific from Satellite Imagery, Climatologies, and a Global Circulation Model
Dale Adolph Kiefer, University of Southern California, Los Angeles, CA, United States, Michael G. Hinton, Inter-American Tropical Tuna Commission, La Jolla, CA, United States, Edward M Armstrong, NASA Jet Propulsion Laboratory, Pasadena, CA, United States, Daniel P Harrison, University of Sydney, Uiversity of Sydney Institute of Marine Science, Sydney, Australia, Dimitris Menemenlis, Jet Propulsion Laboratory, Pasadena, CA, United States and Chen HU, Wuhan University, School of Water Resources and Hydropower Engineering, Wuhan, China
Abstract:
With support from NASA’s Ecological Forecasting program, we have developed a Tuna Stock Assessment Support System, which merges time series of satellite imagery, a global ocean circulation model, climatology from field surveys, and fisheries data on catch and effort. The purpose of this software is to extract information on the habitat of skipjack, bigeye, and yellowfin tuna in the Eastern Tropical Pacific. The support system is based upon a 50-year record of catch and effort from long-line and purse seine vessels provide by the Inter-American Tropical Tuna Commission. This database, which covers thousands of kilometers of ocean surface, provides monthly information at a 1 degree spatial resolution for the purse seine fleet and 5 degree resolution for the long line fishery. This data is then merged in time and space with satellite imagery of sea surface temperature, chlorophyll, and height, as well as NODC climatologies of oxygen concentration and temperature, and output from NASA’s ECCO-2 global circulation model, which provides 3-dimensional simulations of water density, current velocity, mixed layer depth, and sea surface height.
Our analyses have yielded a broad range of understanding of the habitat and dynamics both the fish and the fisherman. The purse seine ground, which targets younger tuna, is constrained to waters where the hypoxic layer is shallow. The longline fishery, which targets older tuna, is not constrained by the hypoxic layer and has a much larger distribution. We have characterized the preferences of each species to environmental variables including the depth of the hypoxic layer, the depth of the water column, as well as sea surface height, temperature, and chlorophyll concentration. Finally, the analyses have revealed information on local depletion by fishing, the size distribution of the schools of younger fish, and the impact of ENSO on fishing activities.
