Reproduction and Embryonic Development of Spiny Dogfish (Squalus acanthias) in the Strait of Georgia, British Columbia

Abstract

Lengths at 50% maturity of spiny dogfish (Squalus acanthias) in the Strait of Georgia, B.C., are 78.5 and 93.5 cm, corresponding to ages 19 and 29 yr, for males and females, respectively. Modal lengths of mature males and females are 85 and 100 cm, respectively.Mating occurs from October to January, with a peak in December. Males are capable of mating every year, with smaller dogfish mating earlier in the year than larger ones. Females mate every 2nd yr. Ovulation of 4 cm diam eggs closely follows mating. The fertilized eggs are enclosed in gelatinous capsules for 4 mo after which the embryos are released into the uterine cavity. The external yolk supply of the embryos is totally absorbed by parturition, although the internal yolk is not fully utilized until 2 mo later. Parturition occurs from September to January, with a peak in November. Gestation is roughly 23 mo. Breeding females produce a mean of 7.14 progeny.These population characteristics indicate that regulation of a future fishery should be by total catch limit rather than net mesh size selection. Key words: spiny dogfish, reproduction, length distribution, survivorship, fecundity, fishery regulation

Reproductive biology ofSqualus acanthiasfrom the east coast, South Island, New Zealand

“…1964Gauld 1979Templeman 1944Nammack et al 1985Bassetal. 1976* Kondyurin & Myagkov 1982Bonham et al 1949Ketchen 1972, 1975Jones & Geen 1977Kaganovskaia 1937Yamamoto & Kibesaki 1949 This study …”

“…Maturity stages were determined following Jones & Geen (1977): Stage 1-Immature: uteri threadlike, no obviously developing ova in the ovaries. Stage 2-Maturing: uteri thickening, but not obviously vascularised, developing ova more or less distinct.…”

“…The left testis was removed, sectioned, and stained with haematoxylin and eosin. For each testis, the proportion of ampullae containing each spermatogenic stage (Simpson & Wardle 1967) was determined on a straight line from the germ ridge to the efferent ductules region (Jones & Geen 1977).…”

Are Density-dependent Effects on Elasmobranch Maturity Possible?

“…Distribution in the Northwest Atlantic extends from Newfoundland to North Carolina and spiny dogfish in this area are considered to represent a single unit population (NEFSC, 1994). The biology of the species has been studied for more than 50 years in all areas where dogfish are found (Kaganovskaia, 1933;Holden and Meadows, 1964;Jensen, 1966;Ketchen, 1972;Ketchen, 1975;Jones and Geen, 1977;Nammack, 1982;Nammack et al, 1985;McFarlane and Beamish, 1987). The last study on reproduction of spiny dogfish in the Northwest Atlantic was conducted in the late-1980s (Silva, 1993).…”

“…A comparison of the highly exploited Scottish-Norwegian stock of spiny dogfish to the lightly exploited Newfoundland stock suggested an increase in fecundity with lower abundance (Templeman, 1944;Holden and Meadows, 1962). Studies of dogfish stocks from the waters of British Columbia showed little change in fecundity in relation to abundance (Bonham et al, 1949;Ketchen, 1972;Jones and Geen, 1977). However, most of the exploitation had occurred prior to any of the studies.…”