PONOMAREVA, L. A. 



1963. Evfauziidy sevemoi poloviny Tikhogo okeana, ikh 

 rasprostranenie i ekologiya massovykh vidov (Euphausi- 

 ids of the North Pacific, their distribution and ecolo- 

 gy). Moscow. Izd. Akad. Nauk SSSR, 142 p. (Translated 

 Isr. Program Sci. Transl., 1966. 154 p.; available U.S. Dep. 

 Commer., Natl. Tech Inf. Serv.. Springfield, Va., as TT 

 65-50098.1 



SpR.'^GUE. J. B. 



1969. Review paper: Measurement of pollutant toxicity to 

 fish. I. Bioassay methods for acute toxicity. Water Res. 

 3:793-821. 



T.-XTTERSFIELD. F., AND H. M. MORRIS 



1924. An apparatus for testing the toxic values of contact 

 insecticides under controlled conditions. Bull. Entomol. 

 Res. 14:585-590. 



species (Lowell 1971; Morris and Kanayama'^l in- 

 dictates that spawning takes place close to shore. 

 The larvae and juveniles lead a pelagic existence 

 for about 3 mo, juveniles moving to shallow in- 

 shore areas at fork lengths (FL) between about 50 

 and 100 mm. The fish become sexually mature 

 males at 20-25 cm FL and subsequently undergo a 

 sex reversal, passing through a hermaphroditic 

 stage and becoming functional females between 

 30 and 40 cm FL. Adults inhabit inshore rocky and 

 sandy areas, frequently in zones of turbulence. 



Methods 



Donovan R. Craddock 



Northtvest and Alaska Fisheries Center- 

 National Marine Fisheries Service. NOAA 

 2725 Montlake Boulevard East 

 Seattle. WA 98112 



LUNAR SPAWNING OF THE THREADFIN, 

 POLYDACrVLL'S SEXFIUS, IN HAWAII' 



Recent evidence indicates that lunar spawning 

 rhythms are more common in fishes than was once 

 thought. Johannes ( 1978) listed 50 species of tele- 

 ost fishes with lunar spawning rhythms, most of 

 them tropical and all of them marine or catadro- 

 mous. In the course of developing methods for cul- 

 turing the threadfin, Polydactylus sexftlis (Cuvier 

 and Valenciennes), we found that this species dis- 

 played a lunar spawning rhythm (May 1976). The 

 lunar pattern of spawning had been indicated by a 

 previous field study (Lowell 1971) and is consis- 

 tent with fishermen's lore (Hosaka 1944), but 

 proof was lacking and details of the rhythm were 

 unknown. In this paper we present detailed infor- 

 mation on the lunar spawning of P. se.x fills along 

 with observations of spawning behavior, using re- 

 sults from captive fish. 



Polydactylus sex fills is a much sought-after food 

 fish in Hawaii and supports an important sport 

 fishery as well as a small commercial fishery 

 (Rao^). Information on the life history of this 



'Contribution No. 552, Hawaii Institute of Marine Biology. 



^Rao, T. R. 1977. Enhancement of natural populations of 

 moi (Polydactylus sexfilis) in Hawaii through the release of 

 hatchery-reared juveniles - a feasibility study of sea ranch- 

 ing. Univ. Hawaii, Hawaii Inst. Mar. Biol., Tech. Rep. 33, 46 p. 

 Hawaii Institute of Marine Biology, P.O. Box 1346, Kaneohe, HI 

 96744. 



Juvenile P. sexfilis were captured by seine on 

 reef flats along windward Oahu in September and 

 October 1970 and reared to sexual maturity in 

 tidal ponds at Coconut Island, in Kaneohe Bay, 

 Oahu. The fish were daily fed chopped squid or 

 smelt, commercial trout chow (409r protein), or 

 trout chow supplemented with chopped squid. In 

 May 1973, 30 mature fish (18 females and 12 

 males) were transferred to a 18-m^ nylon net en- 

 closure suspended from Styrofoam'* floats and an- 

 chored off the leeward (southwest) side of Coconut 

 Island. In June and July 1973, a small number of 

 these fish were removed to laboratory tanks and 

 used in experiments on hormone-induced spawn- 

 ing. During this work, ovarian biopsy samples 

 were examined which contained residual eggs and 

 indicated that the fish had been spawning spon- 

 taneously. In order to monitor any such spawning, 

 an airlift egg collector was installed (May et al.^) 

 in the center of the net in July 1973 and operated 

 continuously (except for a few days when equip- 

 ment malfunctioned) between 14 July 1973 and 31 

 December 1975. Polydactylus sexfilis produces 

 pelagic eggs, so that the collector obtained a sam- 

 ple of eggs at each spawning. Every morning the 

 entire contents of the collector were harvested and 

 examined under a dissecting microscope, and the 

 number of P. sexfilis eggs was estimated by sub- 



^Morris, D. E., and R. Kanayama. 1964-69. Life history 

 study of the moi, Polvdactvlus sexfilis. Job Completion Rep., 

 Projects No. F-5-R-li to F-5-R-17, Div. Fish Game, State of 

 Hawaii. Division of Fish and Game, Honolulu, Hawaii. 



■•Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



■■^May, R. C, G. 8. Akiyama, and M. T. Santerre. 1976. A 

 simple method for monitoring the spawning activity offish in net 

 enclosures. International Milkfish Workshop-Conference, 

 May 19-22, 1976, Tigbauan, Iloilo, Philipp. Working Pap. 10, p. 

 133-138. Southeast Asian Fisheries Development Center, 

 Kalayaan Building, Dela Rosa corner Salcedo Sts., Makati, 

 Metro Manila, Philipp. 



900 



FISHERY BULLETIN: VOL. 76. NO 4, 1979. 



