Evidence of daily spawning in natural populations of the New Zealand snapper Pagrus auratus (Sparidae)

Abstract

SynopsisNew Zealand snapper, Pagrus auratus, were captured by trawling from NE New Zealand over two successive spawning seasons, and examined for acute temporal changes in gonad condition. Fish with oocytes completing final oocyte maturation predominated during the morning, with a peak in ovulated fish occurring just after midday. Afternoon catches were dominated by fish in which the most advanced oocytes had yet to begin final maturation. This suggests that ovulation is synchronised to occur soon after midday, and the high proportion (up to 100% of the catch) of fish with particular gonad stages captured at any one time indicates that daily spawning involves most of the population. Diurnal changes in oocyte diameter support a daily spawning rhythm, with numbers of large hydrated oocytes peaking in the late morning, followed by the disappearance of these oocyte stages in the afternoon. Snapper captured alive by longlining were returned to the laboratory to examine the relationship between ovulation and probable time of spawning. Unovulated fish generally ovulated close to midday on the day of capture (morning captures), or the following day (afternoon captures). The viability of ovulated eggs (proportion undergoing division after fertilization) decreased markedly after oviduct residence times of over 8 hours. This suggests that natural spawning occurs before the late evening. The results of this study are consistent with anecdotal evidence suggesting that spawning occurs every day during the late afternoon or early evening, and is similar to the reproductive patterns displayed by a number of closely related sparids.

Snapper Pagrus auratus (Sparidae) home range dynamics: acoustic tagging studies in a marine reserve

“…data). The characteristics of these movements were consistent with the daily and seasonal patterns that snapper exhibit while spawning (Scott et al 1993). While it is not possible to discern the reason for these movements from this analysis, it is possible that: (1) North Reef was the site of a localised spawning aggregation within the reserve; and (2) structures such as North Reef could be used as a geographic marker for historic spawning aggregations.…”

Reproductive potential of Pagrus pagrus (Perciformes: Sparidae) in coastal waters of Buenos Aires Province (Argentina) and Uruguay (34º-39ºS)

“…Other sparids exhibit daily spawning include the Bluespotted Seabream Pagrus caeruleostictus (Stepkina, 1973), Gilthead Bream Sparus auratus (Zohar, Gordin, 1979), Squirefish Chrysophrys auratus (Scott et al, 1993), and Yellow Seabream Dentex hypselosomus (Yoda, Yoneda, 2009). Our spawning frequency estimates were higher than those reported for other species of the BCE like as M. furnieri (3-5 days; , Cynoscion guatucupa (6-8 days; Militelli et al, 2013) and P. brasiliensis (6 days; Militelli, Macchi, 2001).…”

Changes in visual morphology through life history stages of the New Zealand snapper,Pagrus auratus

“…Spawning occurs in spring and early summer. Repeat daily spawning events occur during late afternoon and early evening, over a period of 3-5 months (Scott & Pankhurst 1992;Scott et al 1993). Snapper display relatively high fecundity (Scott 1991), producing small pelagic eggs which, because of the constraints imposed by small egg volume (and therefore small yolk volume), hatch after a short incubation period, and at a small size (2 mm standard length, SL) (Pankhurst et al 1991).…”