Date of Award

Fall 9-26-2018

Document Type

Thesis

Degree Name

MS Marine Science

Department

Environmental and Ocean Sciences

Committee Chair

Michael G. Hinton

Committee Member

Andrew R. Thompson

Committee Member

Zhi-Yong Yin

Abstract

Overexploitation and climate change can reduce the abundance and shift the spatial distribution of marine species. Determining the habitat suitability of a mobile pelagic species, such as Makaira nigricans (BUM) and Istiompax indica (BLM), can help describe their spatiotemporal distribution patterns over a broad spatial scale, which is a crucial need for fisheries management. Using 14 years (1997-2010) of Inter-American Tropical Tuna Commission (IATTC) catch data from purse-seine vessels in the eastern Pacific Ocean (EPO), we modeled the dynamic habitat suitability of BUM and BLM in response to environmental variables within the EPO using a species distribution model (MaxEnt) with occurrence data (n = 29,711) matched with high resolution remotely sensed oceanographic data. The spatial distribution of suitable habitat for BUM and BLM varied seasonally and in response to El Niño–Southern Oscillation (ENSO) and correlated positively with chlorophyll-a concentrations (CHLA) and sea surface temperature (SST). Seasonal suitable habitat shifted between coastal (winter and spring) and oceanic (summer and fall) waters. During La Niña events, habitat suitability extended well offshore along the equator, whereas during El Niño suitable habitat shifted nearshore to the northern and southern waters of the EPO. Analyses on species’ centers of distribution (CSH) revealed that strength of ENSO events had a strong influence on displacing both species distribution closer or farther from shore. Our findings suggest that if climate change continues in the EPO, the suitable habitat of mobile pelagic species may shift shoreward, potentially making them more accessible to recreational anglers and increasing mortality rates.

Available for download on Thursday, September 26, 2019

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