CalCOFI Reports, Vol. 30, 1989 - California Cooperative Oceanic ...

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LEONG: ANCHOVY SPERM CONCENTRATIONS AND FERTILIZATION RATES CalCOFl Rep.,Vol. 30,1989 Trial TABLE 2 Estimated Density of Sperm and Percentage of Eggs Fertilized When Anchovy Were Induced to Spawn in the Laboratory Estimated sperm density in water of spawning tank (n/ml-')' 1 90 13 2 1435 3 862 1 711 5 337 Number of fish Percentage of eggs fertilized Male" Female 93 0 17 19 98 0 1 19 98 0 18 - 80 1 14 11 99 0 14 18 Average male gonosomatic index ("/o)' 7.8 6.4 4.7 6.1 10.9 6 7 8 9 10 268 217 165 141 122 90.0 70.1 80.0 84.6 96.4 25 6 1 17 18 35 20 16 14 17 8.7 10.1 8.6 7.3 8.3 11 12 13 14 I5 97 87 86 78 66 97.0 81.0 89.2 70.0 60.2 19 11 27 8 13 16 22 14 IO - 3.7 6.9 7.9 8.0 9.4 16 55 80 0 8 16 17 50 54 2 - 3 14 18 25 18 5 11 16 19 4 44 - 3 15 'Estimated froin three 100-mi water saiiiplcs from spaniiiiig tank Containing 2 96 111' water 'Average iiiale length was 116 6 iiim, average weight mas 21 0 g 'Postspawning testes weight - body Lveight X 100 8.3 4.8 5.1 13.0 tioiis in the iiiduced spawning procedure, which in some cases may have stimulated the release of immature gametes. The rough relatioiiships between sperm density and the number of males suggest that the number of sperm released per male was highly variable. The average concentration of sperm in the water may not be the same as the concentration surrounding newly extruded ova. 111 niany species the male deposits sperm directly over the newly spawned eggs (Breder and Rosen 1966), and in those situations the eggs are surrounded by sperm at a much higher concentration than that surrounding the average egg in the water column. However, I did not see any close interaction between the sexes during the trials. Members in the spawning school usually milled about slowly and did not display any obvious behavior patterns such as pairing or posturing to indicate that spawning was in progress; yet my samples indicated that spawning had occurred. The sexes may have simply released gametes into the water, perhaps with some synchrony but without apparent change in behavior. If the spawning anchovy simply released gametes into the water without pairing and body contact, then the eggs were fertilized in water containing the observed sperm concentrations. Whether the simple mode of spawning I observed in the laboratory also occurs in the sea is unknown. Anchovy spawn only at night (Smith and Hewitt 1985; Bolin 1936), and the dark conditions could possibly limit the use of visual cues in their spawning behavior. The minimum sperm density needed for maximal fertilization success has been studied in only a few teleosts, and the results have been varied. Ginzburg (1972) studied the problem by placing roe with ,(1.435) 0 I I Y 0 100 200 300 > 400 SPERM DENSITY (n rnl -I) Figure 2. Percentage of eggs fertilized and sperm density during induced spawning of northern anchovy. Density is number of sperm mi-' water of spawning tank. Densities greater than 400 mi-' are in parenthesis.
LEONG: ANCHOVY SPERM CONCENTRATIONS AND FERTILIZATION RATES CalCOFl Rep., Vol. 30,1989 stripped milt in various dilutions and found that concentrations of 10i-lO" sperm nil- were necessary for maximum fertilization in certain salmonids and sturgeon. In a different setting Hourston and Rosenthal (1976) sampled surface water of milky discoloration above a school of spawning herring Clupcu huwigus yulusii and found concentrations of 148 and 129 sperm m-I, which they theorized to be more than ample for high fertilization success.' The sperm densities at which niaxiniuni fertilization occurred in the present study are close to those observed by Hourston aiid Rosenthal, but magnitudes lower than those observed by Ginzburg. Additional studies would be required to resolve these differences. In any future work, other factors such as swimming speed aiid longevity, length of time ova are receptive to sperm, properties in the egg that may attract or activate sperm, arid temperature should be considered as well as sperm density; only sperm density was coiisidered in this study. 'Hourston and Rosenthal calculated that a herring egg would attract 24 sperm when the density is 150 nil ', but P. E. Smith, NMFS, La Jolla, personal communication, found an error in their calculation; the number attracted should be corrected to 0.024. ACKNOWLEDGMENTS I thank Tohn Hunter, Paul Smith, and Gail Theilacker for- reviewing the maiiuscript and making useful suggestions, aiid Eric Lynn for his help during the trials. LITERATURE CITED Bolin, R. L. 1936. Embryonic and early larval stages of the California anchovy, Gicqraiilis I J I O J ~ Girard. Y Calif. Fish Game 22(1):311-321. Brcder, C. M.. Jr., and D. E. Rosen. 1966. Modes of reproduction in fishes. New York: Natural History Press, Y4l pp. Ginzburg, A. S. 1972. Fertilization in fishes and the problem of polyspermy. Jerusalem: Keter Press. Translated from Russian. Available from U.S. Department of Comnierce, NTIS, Springfield, Virginia, 366 pp. Hourston, A. S., and H. Rosenthal. 1076. Sperm density during active spaivning of Pacific herring (Clirpcn I~OWIJ~IIS pollmi). J. Fish. Res. Board Can. 33:1788-1790. Leong, R. 1971. Induced spawning of the northrrn anchovy, Gigmilis rriordns Girard. Fish. Bull., U. S. 69(2):357-360. Moser, H. G., and E. H. Ahlstroni. 19%. Staging anchovy eggs. IJJ An egg production method for estimating spawning biomass of pelagic fish: application to the northern anchovy, Ei~~pitliz. tizo~da.~, R. Lasker, ed. U.S. Ikp. Coninier., NOAA Tech. Rep. NMFS-36, pp. 37-41. Smith. P. E., and R. 1'. Hewitt. 1985. Sea survey design 2nd analysis for an egg production tnethod of anchovy biomass assessnient. Iii An egg production method for estin~atlng spawning biomass of pelagic fish: application to the northern anchovy, Eti,graiili.i 117or.dns, R. Lasker, ed. U.S. Dep. Commer.. NOAA Tech. Rep. NMFS-36, pp. 17-26. 139
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Cooperative Oceanic Fisheries Inves
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CALCOFI COORDINATOR Gail Theilacker
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COMMITTEE REPORT CalCOFl Rep., Vol.
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FISHERIES REVIEW: 1988 CalCOFl Rep.
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PUBLICATIONS CalCOFl Rep.,Vol. 30,1
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SYMPOSIUM INTRODUCTION CalCOFl Rep.
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POLOVINA: ARTIFICIAL REEFS: BENTHIC
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BUCKLEY: ENHANCING MARINE FISHERIES
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MACCALL: AGAINST MARINE FISH HATCHE
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RUTLEDGE: TEXAS MARINE HATCHERY PRO
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RUTLEDGE: TEXAS MARINE HATCHERY PRO
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