We report the discovery of an enigmatic, small eel-like fish from a 35 m-deep fringing-reef cave in the western Pacific Ocean Republic of Palau that exhibits an unusual suite of morphological characters. Many of these uniquely characterize the Recent members of the 19 families comprising the elopomorph order Anguilliformes, the true eels. Others are found among anguilliforms only in the Cretaceous fossils, and still others are primitive with respect to both Recent and fossil eels. Thus, morphological evidence explicitly places it as the most basal lineage (i.e. the sister group of extant anguilliforms). Phylogenetic analysis and divergence time estimation based on whole mitogenome sequences from various actinopterygians, including representatives of all eel families, demonstrate that this fish represents one of the most basal, independent lineages of the true eels, with a long evolutionary history comparable to that of the entire Anguilliformes (approx. 200 Myr). Such a long, independent evolutionary history dating back to the early Mesozoic and a retention of primitive morphological features (e.g. the presence of a premaxilla, metapterygoid, free symplectic, gill rakers, pseudobranch and distinct caudal fin rays) warrant recognition of this species as a ‘living fossil’ of the true eels, herein described as Protanguilla palau genus et species nov. in the new family Protanguillidae.

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Variations in patterns of daily changes in otolith increment widths of 0+ Pacific saury, Cololabis saira, off Japan by hatch date in relation to the northward feeding migration during spring and summer ABSTRACT Daily changes in otolith increment widths from the core to the edge in 0+ Pacific saury, Cololabis saira, were examined. There appeared a first peak of increment width at 22.9 ± 9.6 (73) [mean ± SD (sample number)] days old, followed by the bottom of the first trough [88.6 ± 25.3 days old (73)] and a second peak [143.8 ± 24.6 days old (62)]. The ages at the second peak formation were strongly related to the estimated hatch dates from 30 October to 7 April (N ¼ 62, r 2 ¼ 0.661) with a negative coefficient of elapsed days from 30 September, corresponding to the beginning of the spawning season. Thus, fish hatched earlier in the spawning season formed the second peak at an older age. The second peak was estimated to occur from 23 April to 14 August, mainly in June and July, at 152.5-216.8 mm (excluding one exception of 96.9 mm) in the earlier period (before 15 June) and at 87.5-177.5 mm in the later period (after 17 June). The peak of otolith increment width is concluded to approximate the peak of daily growth because the relationship between otolith radius and body size was expressed as an allometric curve. The occurrence of the second peak of increment width (growth) can be theoretically explained by descending temperature and ascending feeding condition, which Pacific saury experiences through the northward feeding migration from the warm and food-poor Kuroshio (subtropical) waters to the cold and food-rich Oyashio (subarctic) waters during spring and summer. The clear relationship between the age at the second peak and hatch date suggests the possibility of estimating hatch dates even of fish that have translucent zones in their otoliths by examining the increment widths from the core to the inner edge of the first translucent zone and specifying the age at the second peak.

The importance of the surf zone as a nursery ground for larval and juvenile fishes has been widely recognized, however the zone has yet to be studied in Mauritius. Recently, the coastal area of the island has been increasingly affected by human activities, especially by tourism. We collected fish samples with a hand pulled seine net during the period of August 2001 to March 2003 to clarify the fish fauna and the dynamics of fishes in the surf zone. Two sampling sites adjacent to river mouth areas and one sampling site adjacent to a mangrove area were selected for comparison of fish fauna in relation to environmental conditions. A total of 9,429 fish larvae and juveniles, representing at least 112 species from 48 families were collected. The abundant species were hardyhead silverside, Atherinomorus lacunosus, bluespot mullet, Valamugil seheli, and Ambassis spp., each contributing 16.2, 12.4, and 11.8% of the total number of individuals, respectively. Estuarine species dominated in the surf zone adjacent to the river mouth areas. Species composition and diversity changed seasonally. The number of fish increased during the rainy season. Species diversity increased at the turn of the seasons from the dry season to the rainy season. We conclude that species composition in each site was affected by environmental factors, such as the scale of the flux from the rivers, which is related to the precipitation. The results indicated that freshwater from the river is a trigger to aggregate larvae and juveniles in the surf zone.

A novel species of the family Alepocephalidae (slickheads), Narcetes shonanmaruae, is described based on four specimens collected at depths greater than 2171 m in Suruga Bay, Japan. Compared to other alepocephalids, this species is colossal (reaching ca. 140 cm in total length and 25 kg in body weight) and possesses a unique combination of morphological characters comprising anal fin entirely behind the dorsal fin, multiserial teeth on jaws, more scale rows than congeners, precaudal vertebrae less than 30, seven branchiostegal rays, two epurals, and head smaller than those of relatives. Mitogenomic analyses also support the novelty of this large deep-sea slickhead. Although most slickheads are benthopelagic or mesopelagic feeders of gelatinous zooplankton, behavioural observations and dietary analyses indicate that the new species is piscivorous. In addition, a stable nitrogen isotope analysis of specific amino acids showed that N. shonanmaruae occupies one of the highest trophic positions reported from marine environments to date. Video footage recorded using a baited camera deployed at a depth of 2572 m in Suruga Bay revealed the active swimming behaviour of this slickhead. The scavenging ability and broad gape of N. shonanmaruae might be correlated with its colossal body size and relatively high trophic position.

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