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Age and growth of alfonsino Beryx splendens (Lowe) were studied using counts of presumed daily incremental growth rings on the transverse section of otoliths of fish collected from the Kanto District, central Japan. Microstructural growth increments were observed from the core to the outermost margin of the broadest of approximately 50 branches formed on the surface of an otolith. Of 98 otoliths examined, 46 were readable. The number of increments and fish lengths ranged from 448 (218 mm fork length [FL]) to 3701 (411 mm FL). The ages of these fish were estimated to be 1 year, 2 months and 10 years, 2 months, respectively, assuming that an increment was formed daily. The von Bertalanffy growth equation combined for males and females was expressed as follows: Lt = 542 {1 − exp [−0.133(t + 2.00)]}, where Lt is fork length (mm) at yearly age t. The results of the present study were compared with those of other researchers who had studied alfonsino from central Japan.

The mitochondrial 16S rRNA gene was amplified by polymerase chain reaction usingtotal DNAas a template from muscle tissues of alfonsino and related fish species of alfonsino belong-ing to the genus Beryx , B.splendens , B.mollis and B.decadactylus . While the sequence of the 16SrRNA gene consisted of 492 nucleotides irrespective of the three species, three, nine and eight inter-specific variations were shown between B.splendens and B.mollis , between B.splendens and B.decadactylus , and between B.mollis and B.decadactylus , respectively. The pelagic eggs, which werecollected off Izu Islands and showed morphological characteristics typical to the genus Beryx wereall identified as those of B.splendens from the nucleotide sequence of the mitochondrial 16S rRNA gene. KEY WORDS: 16S rRNA , alfonsino, Beryx , mitochondrial DNA, pelagic eggs, species identification. *Corresponding author: Tel: 81-468-82-2313. Fax: 81-468-81-7903. Email: akimoto@agri.pref.kanagawa.jpReceived 28 December 2001. Accepted 4 June 2002.

SUMMARY: This paper estimates the age and growth of the alfonsino Beryx splendens in the waters around the Izu Islands off the Pacific side of Japan. The samples consist of 250 fish of the landings of the offshore longliners from December 1995 to November 1996 and 10 fish of the coastal longliners in February of 1995. By the surface method using a microscope, a reader counted the number of hyaline and opaque zones on the sagittal otoliths, judged whether the edge was hyaline, and measured the radii from the focus to the outer edge of each hyaline zone. In order to estimate the parameters of the von Bertalanffy’s growth equation representing the overall ages, the age and fork length data and the mean length at 1 year old. In a previous study were used for the maximum likelihood approach. From the results, the rate of readability of the otolith from the offshore samples was 97.6% and that from the coastal samples was 100%. The monthly changes in the frequency of the opaque edge showed that the hyaline and opaque zones were laid down once a year. The hyaline zone began to form from May to July (peaking in August). The ages of the offshore samples for both the sexes ranged from 2 to 23 years, and those of the coastal samples 2 to 5, respectively. The estimated growth curves were expressed by l(t) = 44.4[1–exp{–0.132(t + 3.45)}] for males and l(t) = 45.0[1–exp{–0.150(t + 2.08)}] for females, where l(t) and t denote the fork length (cm) and the age in years, respectively. The issues to be resolved in the future were discussed.