Lipid and fatty acid dynamics by maternal Pacific bluefin tuna

Yuko Hiraoka,Takuya Sato,Yumi Okochi,Yasuhiro Ando,Seiji Ohshimo,Hiroshi Ashida,Tamaki Shimose,Antonio Medina Guerrero

doi:10.1371/journal.pone.0222824

Yuko Hiraoka, Takuya Sato + Show 6 more

Open Access

https://doi.org/10.1371/journal.pone.0222824

Copy DOI

Abstract

Lipid and fatty acid composition of female Pacific bluefin tuna (PBF, Thunnus orientalis) reproductive and somatic tissues in southwestern North Pacific and Sea of Japan spawning grounds are compared. Total lipid (TL) levels are higher in liver than white muscle tissues. An increased gonadosomatic index (GSI) during the early spawning season coincided with decreased TL. Levels of triacylglycerols (TAG) in PBF liver tissues from the Nansei Islands and Sea of Japan, and white muscle in fishes from the Sea of Japan, decreased during the spawning season, while TAG in ovary tissues did not. Concurrent reductions in TL and increases in GSI early in the spawning season suggest TAG depletion was caused by allocation from liver and white muscle tissues to oocytes, that the liver is one of the important lipid-storage organs in PBF, and this species mostly reliant on capital deposits as a mixed capital-income breeder. Differences of docosahexaenoic acid (DHA) levels between spawning grounds were lower in ovary than in muscle and liver tissues. However, eicosapentaenoic (EPA) and arachidonic acid (ARA) levels that influence egg development and embryo and larval growth are significantly higher in PBF tissues from the Sea of Japan than Nansei Islands, which coincided with larval quality. These suggest a maternal effect exists, with egg quality influencing offspring survival, and that the reproductive strategy of PBF varies according to local variation at each spawning ground.

Highlights

Pacific bluefin tuna (PBF, Thunnus orientalis), stocks of which are exploited by many countries, is one of the most valuable fisheries species in the world [1]
Variation in Total lipid (TL) and gonadosomatic index (GSI) depending on year, area and oocyte developmental stage
Developing oocytes can obtain lipids from three possible sources: 1) exogenous, supplied through the maternal diet, 2) endogenous, mobilised from adipose fat, and 3) those synthesised de novo in the ovarian follicle from small organic precursors or fatty acids mobilised and transported from other tissues [13, 39]

Summary

Introduction

Pacific bluefin tuna (PBF, Thunnus orientalis), stocks of which are exploited by many countries, is one of the most valuable fisheries species in the world [1]. Recent stock assessments have indicated the current PBF spawning-stock biomass to be near a historic low, and the stock to be overfished [2]. Despite the low spawning-stock biomass, no previously observed [2] clear decline in PBF recruitment is apparent. Lipids and fatty acids of Pacific bluefin tuna

Objectives

Methods

Results

Conclusion