Early life history of a seahorse, Hippocampus mohnikei, in Tokyo Bay, Japan

Authors
Citation
K. Kanou et H. Kohno, Early life history of a seahorse, Hippocampus mohnikei, in Tokyo Bay, Japan, ICHTHYOL R, 48(4), 2001, pp. 361-368
Citations number
20
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Animal Sciences
Journal title
ICHTHYOLOGICAL RESEARCH
ISSN journal
1341-8998 → ACNP
Volume
48
Issue
4
Year of publication
2001
Pages
361 - 368
Database
ISI
SICI code
1341-8998(20011126)48:4<361:ELHOAS>2.0.ZU;2-F
Abstract
The early morphological development, seasonal and spatial occurrence patter ns, and food habits of a seahorse, Hippocampus mohnikei, in offshore waters of Tokyo Bay, central Japan, were studied on the basis of 206 juvenile and young specimens (6.0-65.3 mm TL) collected between August 1995 and January 1999. All the specimens were collected within the period from May to Janua ry, inclusive, each year. In the least developed specimen (6.0 mm TL), the number of dorsal, anal, and pectoral fin rays had attained the adult comple ment, whereas the minute caudal fin, consisting of two rays, was present in juveniles of 6.0-26.4 mm TL. Hippocampus mohnikei greater than or equal to 35 mm TL, being larger than settlement size (ca. 30 mm TL), had very low g ut fullness index values (GFI = 0, >70% of specimens), whereas those of 15- 29 mm. TL had higher values (GFI = 2-4, >80% of specimens). In addition, la rger individuals selectively fed on larger planktonic animals (species of B rachyura), which occurred naturally at low densities, although smaller food items, such as Oithona davisae and Penilia avirostris, occurred abundantly , being consumed by smaller H. mohnikei individuals (15-34 mm TL). These re sults indicated that food availability for H. mohnikei in offshore waters o f Tokyo Bay is significant for individuals larger than settlement size. bec ause their food preference would shift from smaller food items to larger fo od items, which would be scarce in their environments.