Western Central Pacific Ocean Research Articles

Subsidies to tuna fisheries in the Western Central Pacific Ocean

Tuna fisheries in the Western and Central Pacific Ocean are among the most valuable resources in the region. These fisheries, worth an estimated $4.1 billion each year, play a pivotal role in supporting incomes and development goals in the region. However, due to the twin, and potentially inter-related effects of harmful fishing practices such as the use of fish aggregating devices, overcapacity, and fisheries subsidies, many of these tuna fisheries are currently at risk of over-exploitation—putting the livelihoods of countless local fishers at risk. This study finds that government fisheries subsidies in the region represent 37% of the ex-vessel value of tuna fisheries in the region. Fuel subsidies are estimated at US$ 335 million and non-fuel subsidies are estimated at US$ 1.2 billion for the year 2009. Developed countries are responsible for more than half of the subsidies spent in the predominantly developing region, underlying the fact that the majority of tuna value extracted from the national waters of developing countries in the region benefit larger, developed countries. The total resource rent, or return to society, from tuna fisheries, once adjusted for subsidies is a net negative US$750 million in 2009. Fisheries subsidies are enabling foreign fleets to operate at sub-market rates, putting local fleets out of competition for their own fishery resources.

Shifting from marine reserves to maritime zoning for conservation of Pacific bigeye tuna ( Thunnus obesus )

Over 50% of the total bigeye tuna (BET) landed in the Western Central Pacific Ocean is caught incidentally in the purse seine fishery and sold for canning at prices less than US$2/kg. The remainder is landed in longline fisheries directed at BET and sold as fresh or frozen tuna at prices greater than US$10/kg. The combined fishing mortality by all gears will soon reduce the BET biomass in the Pacific Ocean to less than that capable of producing maximum sustainable yield. Closure of the high-seas enclaves in 2009 was hailed as a conservation measure, but was not scientifically evaluated before implementation and appears to have had no beneficial effect on the BET stock. A spatially explicit age-structured ecosystem model, SEAPODYM, is used to simulate alternative area-based fishery management policies to conserve bigeye tuna in the Western Central Pacific Ocean. Closing the high-seas enclaves to purse seine fishing has negligible effect on the BET biomass. Fishery management policies that control mortality on both juveniles and adults, through prohibition of fish aggregation devices in the purse seine fishery and restrictions on longline fishing in spawning areas, are the most efficient conservation policies. Large-scale benefits from bigeye conservation measures will become apparent only in the 2030s, assuming timely implementation and minimal effects of climate change.

Modelling the impact of climate change on Pacific skipjack tuna population and fisheries

IPCC-type climate models have produced simulations of the oceanic environment that can be used to drive models of upper trophic levels to explore the impact of climate change on marine resources. We use the Spatial Ecosystem And Population Dynamics Model (SEAPODYM) to investigate the potential impact of Climate change under IPCC A2 scenario on Pacific skipjack tuna (Katsuwonus pelamis). IPCC-type models are still coarse in resolution and can produce significant anomalies, e.g., in water temperature. These limitations have direct and strong effects when modeling the dynamics of marine species. Therefore, parameter estimation experiments based on assimilation of historical fishing data are necessary to calibrate the model to these conditions before exploring the future scenarios. A new simulation based on corrected temperature fields of the A2 simulation from one climate model (IPSL-CM4) is presented. The corrected fields led to a new parameterization close to the one achieved with more realistic environment from an ocean reanalysis and satellite-derived primary production. Projected changes in skipjack population under simple fishing effort scenarios are presented. The skipjack catch and biomass is predicted to slightly increase in the Western Central Pacific Ocean until 2050 then the biomass stabilizes and starts to decrease after 2060 while the catch reaches a plateau. Both feeding and spawning habitat become progressively more favourable in the eastern Pacific Ocean and also extend to higher latitudes, while the western equatorial warm pool is predicted to become less favorable for skipjack spawning.

Development of Bayesian production models for assessing the North Pacific swordfish population

Bayesian surplus production models were developed for assessing the North Pacific swordfish population under alternative scenarios: a single-stock scenario and a two-stock scenario with subareas that represented the western central and eastern Pacific Ocean regions. Biomass production was modeled with a three-parameter production model that allowed production to vary from the symmetric Schaefer curve using an estimated shape parameter. Lognormal prior distributions for intrinsic growth rate and carrying capacity were assumed. Goodness-of-fit diagnostics were developed for comparing the fits of alternative model configurations based on the root-mean squared error of catch per unit effort (CPUE) fits and the standardized CPUE residuals. Production model fits for 1952–2006 indicated that the Japanese longline CPUE numbers were influential under each stock scenario because these scenarios were the longest time series of relative abundance indices. Model results also indicated that assumptions about the prior means for intrinsic growth rate and carrying capacity may be important based on the model configuration.

Timing of El Niño–Related Warming and Indian Summer Monsoon Rainfall

Abstract The relationship between all-India summer monsoon rainfall (ISMR) and the timing of (El Niño–Southern Oscillation) ENSO-related warming/cooling is investigated, using observational data during the period from 1881 to 1998. The analysis of the evolutions of Indo-Pacific sea surface temperature (SST) anomalies suggests that when ISMR is not below normal despite the co-occurrence of an El Niño event, warming over the eastern equatorial Pacific starts from boreal winter and evolves early so that the western-central Pacific and Indian Ocean are warmer than normal during the summer monsoon season. In contrast, when the more usual El Niño–dry ISMR relationship holds, the eastern equatorial Pacific starts warming rapidly only about a season before the reference summer so that the western-central Pacific and Indian Oceans remain cold during the monsoon season.

卵巣の組織学的観察による中西部熱帯太平洋におけるカツオの成熟と産卵生態の推定

中西部熱帯太平洋における本種の卵巣組織観察から，成熟と産卵生態を推定した。半数成熟体長は 47.9 cm で，核移動期をもつ個体は 15-21 時に採集されたものに限られた。同一の生殖腺指数（GI）階級において成熟段階の異なる個体が存在することから，GI は卵巣成熟度を正確に反映できないと推察した。成熟個体の卵巣は常に周辺仁期が約 80% 以上を占めており，卵黄球期以降の卵母細胞は 5～10% であった。周年に亘り大半の成熟個体が産卵段階，産卵移行段階であり，産卵停止段階の出現が少なく，周年産卵を行うと推察した。

Apparent biological fractionation between Cd and PO 4 in the surface waters of the equatorial Pacific Ocean

Apparent biological fractionation between cadmium (Cd) and phosphate (PO 4) in seawater from 10 to 200 m in the western and central equatorial Pacific was examined in January 2003 at nine stations. In this study period, a surface salinity front existed at approximately 175°W, dividing oceanographic conditions into two types: the Western Pacific Warm Pool (WPWP) (westward) and the eastern upwelling zone (eastward), and, at a depth of approximately 100–150 m, a thermocline developed, separating the surface water from the nutrient-rich deep water. Based on the temperature distribution, three types of water masses were defined: within the WPWP (> 29.2 °C), outside the WPWP above the top of the thermocline (the top of the thermocline is the water depth at which the temperature is 1 °C lower than the surface temperature), and below the top of the thermocline, generally corresponding to PO 4 concentrations of less than 0.25 μM, from 0.25 μM to 0.50 μM, and over 0.50 μM, respectively. The fractionation coefficient values were determined to be 0.36, 1.09, and 1.68 for the three layers defined, respectively, on the assumption that the uptake and regeneration processes of Cd and PO 4 by the biological activity obeyed first-order reaction kinetics. Similarly, Hagino et al. (2000) [Hagino, K., Okada, H., Matsuoka, H. (2000). Spatial dynamics of coccolithophore assemblages in the Equatorial Western-Central Pacific Ocean. Marine Micropaleontology 39, 53–72] have previously found that planktonic coccolithophorid assemblages in these waters also differ between these water masses, presumably discriminating among the three layers when selecting their habitat. By analogy, I speculate that the fractionation coefficient between the two constituents Cd and PO 4 varies according to differential uptake/regeneration of the species assembly in these populations of primary producers (and grazers), where sheer biomass and environmental conditions likely also play a role.

Tropical sea‐surface temperature reconstruction for the early Paleogene using Mg/Ca ratios of planktonic foraminifera

To understand the climate dynamics of hypothesized past greenhouse intervals, it is essential to constrain tropical sea‐surface temperatures (SST), yet existing proxy records give conflicting results. Here we present the first Mg/Ca‐based study of pre‐Quaternary SST and investigate early Paleogene (late Paleocene through late middle Eocene; 58.6–39.8 Ma) tropical temperatures, using planktonic foraminifera belonging to the genus Morozovella from Ocean Drilling Program Site 865 on Allison Guyot (western central equatorial Pacific Ocean). Calcification temperatures similar to or warmer than modern tropical SST are calculated using a range of assumptions regarding diagenesis, temperature calibration, and seawater Mg/Ca. Long‐term warming is observed into the early Eocene (54.8–49.0 Ma), with peak SST between 51 and 48 Ma and rapid cooling of 4°C beginning at 48 Ma. These findings are inconsistent with the δ18O‐based SST previously estimated for this site.

CHANGES IN MODELS OF AQUATIC ECOSYSTEMS APPROACHING CARRYING CAPACITY

Using a top-down modeling approach, published mass-balance models of trophic interactions and state variables in the western central Pacific Ocean and the northern Gulf of Mexico shelf were used to explore how large increases in top predator biomasses can be accommodated with given primary productions. It appears that the biomasses of top predators in these models can be increased an order of magnitude, which leads to a six- to sevenfold increase in overall consumer biomasses. This results in changes in food web structures that are in agreement with major aspects of E. P. Odum's theory of ecosystem development, particularly with regard to features associated with the retention and recycling of detritus. Based on the simulations and Odum's theory, we propose a functional definition of carrying capacity: the upper limit of biomass that can be supported by a set primary production and within a variable food web structure is reached when total system respiration equals the sum of primary production and detrit...

METAROTALIELLA TUVALUENSIS SP. NOV. FROM FUNAFUTI ATOLL, WESTERN PACIFIC OCEAN: RELATIONSHIP TO MILIOLID FORAMINIFERA

Metarotaliella tuvaluensis n. sp. is described from shallow lagoon sediments of Funafuti Atoll, western central Pacific Ocean, where it is found attached to Triloculina barnardi and, less commonly, to Quinqueloculina laevigata and Q. oblonga. Metarotaliella tuvaluensis attaches to the tests of partly-grown miliolid individuals; responses of the latter include attempts to overgrow or surround M. tuvaluensis , malformation of the chamber added after the attachment, and modification of the external test ornamentation. Growth of the test walls of the miliolid onto the M. tuvaluensis test holds the latter firmly in position and may eventually completely envelope it. Sexual reproduction of M. tuvaluensis is by plastogamy in place on the miliolid test, involving two or more gamonts of unequal size, and the miliolid probably survives this. The relationship may be a fortuitous one of the rotaliine simply attaching to an available substrate, or alternatively may be an example of endoparasitism. It is rare, affecting less than 3% of the adults of the miliolid species involved, and, even if harmful, is therefore unlikely to have a significant effect on the population dynamics of the miliolids.

The development of the Palau Arrangement for the management of the Western Pacific Purse Seine Fishery

In the early 1990s, island States of the South Pacific, confronted with the need to develop appropriate arrangements to enable them to manage highly migratory fish stocks in the western central Pacific ocean, developed the Palau Arrangement for the Management of the Western Pacific Purse Seine Fishery. This paper traces the development of the Palau Arrangement from a legal and political perspective. The implementation of the Arrangement has led to tension between coastal States and States fishing in the region which will need to be resolved if both sides are to fulfil the duty to cooperate in the management of highly migratory fish stocks under LOSC and the 1995 Agreement on Straddling Fish Stocks and Highly Migratory Fish Stocks.

Late Jurassic and Early Cretaceous evolution of the Western Central Pacific Ocean.

Late Jurassic and Early Cretaceous evolution of the Western Central Pacific Ocean.