Pubblicazione scientifica

Structure and properties of the egg mass of the ommastrephid squid Todarodes pacificus

FILONE TECNOLOGICO	TEMA
produzione e raccolta

RIASSUNTO

The Japanese flying squid, Todarodes pacificus, is thought to spawn neutrally buoyant egg masses that retain a specific location in the water column by floating at the interface between water layers of slightly different densities. It is important to understand the physical process that determines the vertical distribution of the egg masses to predict their horizontal drift in relation to embryo survival and subsequent recruitment. Here, mesocosm experiments were conducted in a 300 m3 tank by creating a thermally stratified (17–22°C) water column to obtain egg masses. A cage net methodology was developed to sustain egg masses for detailed observation. We measured the density of the egg masses of T. pacificus, and used this information to infer the vertical distribution patterns of the egg masses at the spawning grounds (Tsushima Strait, Japan). When measured separately, the density of the outer jelly of each egg mass was 2.7 σ units higher than that of the surrounding water. The outer jelly and the specific gravity of embedded individual eggs (~1.10) cause the egg masses to have very slight negative buoyancy relative to the water in which they are formed. Analysis of the vertical profile of the spawning ground showed that water density (σθ) increased sharply at ~30 m depth; thus, egg masses might settle above the pycnocline layer. In conclusion, we suggest that T. pacificus egg masses might retain their location in the water column by floating at the interface between water layers of slightly different densities, which happen to be above the pycnocline layer (actual depth varies seasonally/annually) in the Tsushima Strait between Korea and Japan.

DATA

Data di pubblicazione: 02/08/2017

AUTORI

PUNEETA PANDEY
VIJAI DHARMAMONY
YAMAMOTO JUN
ADACHI KOHSUKE
KATO YOSHIKI
SAKURAI YASUNORI

ENTE DI AFFERENZA

DEPT MARINE BIORESOURCES & ECOLOGY SCHOOL OF FISHERIES SCIENCES HOKKAIDO UNIV HAKODATE JAPAN
FIELD SCIENCE CTR NORTHERN BIOSPHERE HOKKAIDO UNIV HAKODATE JAPAN
LAB OF AQUATIC PROD UTILIZATION GRADUATE SCHOOL OF AGRICULTURE KOCHI UNIV MONOBEOTSU 200 NANKOKU KOCHI JAPAN
MARINE FISHERIES RSCH & DEV CTR JAMARC JAPAN FISHERIES RSCH & EDUCATION AGENCY YOKOHAMA CITY KANAGAWA JAPAN
UNIV SHIGA PREFECTURE JAPAN

RIVISTA

PLoS ONE, 12(8), e0182261

IMPACT FACTOR

2,870

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