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Notes: Abstract A study was made on the vertical distribution of Chaetognatha in the Hilutangan Channel, based on analyses of 48 plankton samples. Thirty-min horizontal plankton tows were performed at depths of 1, 20, 50, 70 and 100 m in January 1972. Thirteen species of 3 genera of maturing and mature chaetognaths were identified and counted. Sagitta inflata was the most common and abundant species (63.0%), folloed by S. neglecta (9.7%), S. robusta (8.6%), S. regularis (5.4%), S. serratodentata (4.2%), Krohnitta pacifica (2.9%), S. bedoti (2.3%) and S. decipiens (2.0%). S. pulchra (0.7%), S. ferox (0.5%), K. subtilis (0.3%), Pterosagitta draco (0.2%) and S. hexaptera (0.2%) were represented by less than 1% each. Of these 13 species in the upper 100 m, 12 were epiplanktonic while one species, S. decipiens, is generally considered to be mesoplanktonic. Three species were classified as neritic, 3 as neritic-oceanic, and 6 as oceanic, indicating the dominant influence and strong influx of oceanic water into the Hilutangan Channel. Temperature, salinity and dissolved oxygen content did not seem to influence the vertical distribution. Examination of gut contents showed that copepods, followed by arrow worms, were most common in the guts of the chaetognaths studied.

Notes: Abstract Specimens of juvenile and mature rabbitfish, Siganus oramin and S. striolata, were submitted to stomach analyses. Agarophytes of the genera Gracilaria, Hypnea and Laurencia proved to be the most preferred diet. Small invertebrates were ingested accidentally.

Notes: Abstract The vertical distribution of euthecosomatous pteropods in the upper 100 m of the Hilutangan Channel, Cebu, The Philippines was studied, based on 126 samples, comprising 47, 282 individuals. Thirty-min horizontal plankton tows were performed at depths of 1, 20, 50, 70 and 100 m in January and February 1972. Thirteen species —including 3 subspecies — of juvenile and adult euthecosomes were identified. In decreasing order of abundance the species are: Creseis acicula (20.4%), Limacina trochiformis (19.9%), Creseis virgula constricta (14.6%), L. inflata (10.5%), Clio pyramidata (9.9%), Creseis virgula conica (8.9%), L. bulimoides (7.3%), Diacria quadridentata (5.3%), Cavolinia longirostris (1.9%), Creseis virgula virgula (1.0%), Hyalocylix striata (0.1%), Cuvierina columella (0.08%), Cavolinia uncinata (0.002%). In 3 species, a large percentage were juveniles; for 1 species, Clio pyramidata, only juveniles were caught. The Vertical species distribution was similar to the distribution of the respective species in Caribbean and Bermuda waters. Temperature, salinity and dissolved oxygen influence vertical distribution little, if at all.

Notes: Abstract Predation of different-sized Hyperoche medusarum (Hyperiida: Amphipoda) on larvae of the Pacific herring Clupea harengus pallasi was studied in the laboratory. The attacking rate of H. medusarum was a function of herring larvae size as well as size of the predator, and varied from 0.15 to 0.95 larvae attacked h-1 per hyperiid. In the range of 7.55 to 16.05 mm total larval length, vulnerability to predation was highest for 13.3 and 13.7 mm larvae. Large hyperiids swam faster and covered a wider area during searching and were more effective predators than small ones. Predation seemed to be influenced by light, and its intensity was dependent on the duration of previous food deprivation of the hyperiid.

Notes: Abstract The utilization and fate of nitrogen in larvae of plaice (Pleuronectes platessa), blenny (Blennius pavo) and herring (Clupea harengus), from the stage of first-feeding to metamorphosis, was examined under laboratory conditions. Rates of ammonia excretion, primary amine defaecation, and growth in terms of protein-nitrogen were monitored throughout larval life. Data were used to calculate daily ration, the coefficient of nitrogen utilization (absorption efficiency), and gross and net growth efficiencies. The developmental pattern of nitrogen balance was similar for plaice and blenny larvae. These species showed increasing growth efficiency (k1: 55 to 80%) with decreasing weight-specific waste nitrogen losses with age. Absorption efficiencies. were high (83 to 98%) in plaice and blenny larvae, and tended to increase with development in the former species. Ration relative to body weight decreased with growth in both species. Herring larval development, although at a slower rate than blenny and plaice, appeared normal up to 33 d, after which high mortality occurred. Absorption efficiency in this species tended to decline (83 to 43%) with age, until metabolic costs exceeded the absorbed ration and growth ceased. Artemia sp. nauplii proved a suitable food source for the rearing of plaice and blenny larvae, but this diet may have long-term toxicity or deficiency effects on herring. Availability and density of food affected nitrogen balance in the larvae of all three species. Feeding stimulated the output of wastes in excretion and defaecation by a factor of up to ten times the 12-h non-feeding basal rates. Waste nitrogen output reached a peak some 2 to 3 h after commencement of feeding and returned slowly to the baseline in 5 to 10 h after cessation of feeding. There was an asymptotic increase in ration, ammonia output and growth of larvae as prey density increased. Ration saturated at a higher prey density (〉4 prey ml-1) than either growth or excretion rate (1 prey ml-1). Thus the efficiency with which food is absorbed and utilized for growth must eventually decline in response to high prey density. The idea that larval fish are adapted to maximize ingestion and growth rate, rather than optimize growth efficiency and thus to respond to prey occurring in either low density or in occasional patches, is supported by these results.