Evidence and patterns of tuna spawning inside a large no-take Marine Protected Area

Abstract

The Phoenix Islands Protected Area (PIPA), one of the world’s largest marine protected areas, represents 11% of the exclusive economic zone of the Republic of Kiribati, which earns much of its GDP by selling tuna fishing licenses to foreign nations. We have determined that PIPA is a spawning area for skipjack ( Katsuwonus pelamis ), bigeye ( Thunnus obesus ), and yellowfin ( Thunnus albacares ) tunas. Our approach included sampling larvae on cruises in 2015–2017 and using a biological-physical model to estimate spawning locations for collected larvae. Temperature and chlorophyll conditions varied markedly due to observed ENSO states: El Niño (2015) and neutral (2016–2017). However, larval tuna distributions were similar amongst years. Generally, skipjack larvae were patchy and more abundant near PIPA’s northeast corner, while Thunnus larvae exhibited lower and more even abundances. Genetic barcoding confirmed the presence of bigeye ( Thunnus obesus ) and yellowfin ( Thunnus albacares ) tuna larvae. Model simulations indicated that most of the larvae collected inside PIPA in 2015 were spawned inside, while stronger currents in 2016 moved more larvae across PIPA’s boundaries. Larval distributions and relative spawning output simulations indicated that both focal taxa spawned inside PIPA in all 3 study years, demonstrating that PIPA is protecting viable tuna spawning habitat.

RETRACTED: A global network of marine protected areas for food

“…While empirical studies have demonstrated spillover benefits for some species (13,15,16,21,50,(57)(58)(59) and provide support for fisheries benefits of both small (57-59) and large (39)(40)(41) MPAs, the majority of the species considered in our analyses lack empirical support (one way or the other) for spillover effects. Furthermore, while we rely only on MPA size as an important aspect of reserve design (25, 60-62), we recognize that other factors, such as MPA geometry, spacing, age, and habitat quality, also affect spillover (14,(63)(64)(65).…”

“…Furthermore, while unaccounted for in our current model, large and remote MPAs may protect ecologically important areas that are vital for certain life history stages of even highly migratory species, which may result in fisheries benefits for target stocks. For example, tuna spawn inside the Phoenix Island Protected Area (39), and there is an increasing body of evidence demonstrating potential fisheries benefits from MPAs for pelagic populations in the Chagos Archipelago (40) and the Galápagos Marine Reserve (41).…”

Complex Dispersal of Adult Yellowfin Tuna From the Main Hawaiian Islands

“…The contrasting movement patterns exhibited by different yellowfin life stages and studies conducted over a decade apart have demonstrated that tuna movement between tropical and temperate regions remains inadequately understood (Holland et al, 1999;Pecoraro et al, 2017Pecoraro et al, , 2018Anderson et al, 2019). As the Central North Pacific faces various anthropogenic stressors (Erauskin-Extramiana et al, 2019;Woodworth-Jefcoats et al, 2019) and stakeholders experience potential changes to fisheries management and conservation measures such as creation of large-scale marine protected areas (Richardson et al, 2018;Hernández et al, 2019), availability of yellowfin tuna and economic impacts to local communities will remain a serious issue.…”

Ecological responses to blue water MPAs

“…While there is limited understanding of spawning behaviors of most pelagic species [ 80 ], bigeye, yellowfin, skipjack and albacore tunas are currently understood to have extensive spawning grounds in tropical and subtropical waters and protracted spawning seasons [ 79 , 81 ]. While tuna spawning habitat very likely occurs within the monument components assessed here and other pelagic MPAs of the tropical Pacific [ 82 ], for these highly fecund broadcast spawners, protecting a small proportion of the distribution of spawning stock biomass likely has minimal effect on recruitment or absolute biomass, where only at extremely low population sizes would egg production likely be a limiting factor for recruitment [ 83 , 84 ]. If individuals are transient, remaining for relatively short time periods (days, weeks) in an MPA, especially if fishing-the-line occurs, then there would not be an increase in biomass from the MPA, locally or stock-wide [ 11 , 20 , 85 – 86 ].…”