Distribution of Alfonsino Beryx splendens Eggs in the Spawning Ground around the Sea Mounts off Izu Islands, Middle Japan.

Abstract

Many alfonsino eggs that had not been collected in the sea were collected in the expected spawning ground around Izu Islands off central Japan from June to August, 1993. The eggs were collected in 5 sampling areas.Most eggs were collected from 2 to 6 a.m., and most were in the Morula to embryo-appearance stages. A few of the most developed eggs which were just about to hatch were collected around the spawning ground. More eggs were collected by a 0-250m tow than by a 0-100m tow, suggesting that the eggs gradually diffused from the spawning ground as development proceeded.

Identification of alfonsino and related fish species belonging to the genus Beryx with mitochondrial 16S rRNA gene and its application on their pelagic eggs

“…Samples collected with the net were fixed with 5% formalin and a rough sorting for eggs belonging to the genus Beryx was carried out by using their morphological characteristics (Table 2). Typically, the pelagic eggs concerned were 1.08–1.22 mm in the whole diameter and 0.16– 0.31 mm in the diameter of the orange‐colored oil globule 10,11 . Sorted eggs were stored in 99.5% ethanol at 4°C and subjected to DNA extraction.…”

“…Several biological features of B. splendens have been documented, including maturity, 2–4 growth, 5–8 distribution of adult fish 9 and spawning grounds 10 . However, other information has not been satisfactorily determined, such as the abundancy, distribution and translocation of pelagic eggs and larvae, and the developmental stage where larvae start moving to the bottom.…”

“…Many efforts have been made to collect large enough quantities of pelagic eggs belonging to B. splendens , but such attempts have not been successful, leaving their local distribution ambiguous. Some of the pelagic eggs collected by using a plankton net in the area near Izu Islands were identified as those of B. splendens by Kuboshima, 10 due to their morphological characteristics, such as diameters of egg and yolk sphere and color of oil globule. However, it is generally difficult to identify species for pelagic eggs by morphological characteristics, especially for those belonging to the same family or genus 11 .…”

“…In the case of Beryx splendens , Beryx decadactylus , and Beryx mollis , the distribution of both adult fish and pelagic eggs appear to overlap each other. In addition, fixation of pelagic eggs with formalin for sorting often leads to transformation of their shape as well as discoloration 10 . As morphological characteristics of eggs from these three species belonging to the genus Beryx are very similar to each other, it is difficult to identify them correctly.…”