Population Dynamics of Spiny Dogfish (Squalus acanthias) in British Columbia Waters

1979 ◽  
Vol 36 (6) ◽  
pp. 647-656 ◽  
Author(s):  
C. C. Wood ◽  
K. S. Ketchen ◽  
R. J. Beamish
Keyword(s):  
British Columbia ◽  
Population Dynamics ◽  
Age Structure ◽  
Squalus Acanthias ◽  
Minimum Size ◽  
Spiny Dogfish ◽  
Natural Mortality ◽  
Structure Model ◽  
Density Dependent ◽  
Sustained Effort

An age-structure model that incorporates recent information regarding growth and reproduction has been developed to investigate the dynamics of spiny dogfish (Squalus acanthias) populations in British Columbia waters. Mechanisms for density-dependent regulation of abundance were evaluated on the basis of theoretical effectiveness and ability to predict observed patterns in simulations of the historical fishery. Compensatory change in the rate of natural mortality appears to be the principal mechanism for density-dependent response. The instantaneous rate of natural mortality at natural equilibrium was estimated to be 0.094 MSY for British Columbia waters is ~ 9000–11 000 t/yr. The minimum size at entry to the fishery has little effect on MSY. Sustained-effort, sustained-yield, and periodic fisheries were modeled to determine optimum harvesting strategies. Periodic fisheries were found to vary widely in feasibility and appear to be impractical from a management perspective whereas a sustained-effort fishery would ensure maximum stability. Key words: spiny dogfish, population dynamics, age-structure model, density-dependence, simulation model, commercial fishing strategies

scholarly journals Increased natural mortality at low abundance can generate an Allee effect in a marine fish

2014 ◽  
Vol 1 (2) ◽  
pp. 140075 ◽  
Author(s):  
Anna Kuparinen ◽  
Jeffrey A. Hutchings
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Density Dependence ◽  
Gadus Morhua ◽  
Allee Effect ◽  
Population Regulation ◽  
Atlantic Cod ◽  
Adult Mortality ◽  
Natural Mortality ◽  
Density Dependent

Negative density-dependent regulation of population dynamics promotes population growth at low abundance and is therefore vital for recovery following depletion. Inversely, any process that reduces the compensatory density-dependence of population growth can negatively affect recovery. Here, we show that increased adult mortality at low abundance can reverse compensatory population dynamics into its opposite—a demographic Allee effect. Northwest Atlantic cod ( Gadus morhua ) stocks collapsed dramatically in the early 1990s and have since shown little sign of recovery. Many experienced dramatic increases in natural mortality, ostensibly attributable in some populations to increased predation by seals. Our findings show that increased natural mortality of a magnitude observed for overfished cod stocks has been more than sufficient to fundamentally alter the dynamics of density-dependent population regulation. The demographic Allee effect generated by these changes can slow down or even impede the recovery of depleted populations even in the absence of fishing.

Food and Feeding of Spiny Dogfish (Squalus acanthias) in British Columbia Waters

1977 ◽  
Vol 34 (11) ◽  
pp. 2056-2066 ◽  
Author(s):  
Barry C. Jones ◽  
Glen H. Geen
Keyword(s):  
British Columbia ◽  
Stomach Content ◽  
Squalus Acanthias ◽  
Spiny Dogfish ◽  
Commercial Catch ◽  
Food Items ◽  
Annual Consumption ◽  
Food And Feeding ◽  
Dietary Components ◽  
Winter Annual

Stomach content data on 14,796 spiny dogfish (Squalus acanthias) from British Columbia waters are presented. The major dietary components based on occurrence were 55% teleosts, 35% crustaceans, and 5% molluscs. The principal food items were herring (22%) and euphausiids (14%). Prey was largely pelagic (80%), with fishes predominating in winter and invertebrates in summer. Fishes became more important in the diet with increasing dogfish size. Dogfish consumed twice as much food in summer as in winter. Annual consumption varied from 5 times biomass for small dogfish to 2.5 times for larger animals. Preliminary analyses suggest that dogfish consume over 5 times the current annual commercial catch of herring, but insignificant quantities of salmon. Key words: dogfish, Squalus, feeding, food, biomass, predation, metabolism, seasonality, survivorship, digestion

sexual maturity, fecundity and embryonic development of the spiny dogfish, squalus acanthias, in the eastern mediterranean sea

2005 ◽  
Vol 85 (5) ◽  
pp. 1155-1161 ◽  
Author(s):  
archontia chatzispyrou ◽  
persefoni megalofonou
Keyword(s):  
Mediterranean Sea ◽  
Eastern Mediterranean ◽  
Gonadosomatic Index ◽  
Squalus Acanthias ◽  
Minimum Size ◽  
Hepatosomatic Index ◽  
Spiny Dogfish ◽  
Female Fish ◽  
Eastern Mediterranean Sea ◽  
Gravid Females

the reproductive biology of the spiny dogfish, squalus acanthias, was investigated throughout a year, in the eastern mediterranean sea. one hundred and eighty specimens were sampled of which 119 were females and 61 males, ranging from 320 to 755 mm and from 350 to 820 mm total length (tl), respectively. the minimum size of mature females was 515 mm and 470 mm tl for mature males (smaller compared with sizes in other studies). gonadosomatic index (gsi) and hepatosomatic index (hsi) were higher during june and august in female dogfish, respectively; in males gsi had a peak in july and hsi showed its highest value in april. a total of 39 gravid females was identified with tl ranging between 570 and 755 mm. only 28 of them were bearing embryos; candled uteri were observed in the 11 other gravid animals. a positive relationship was recorded between maternal length and litter size. ovarian fecundity ranged between 1 and 6 (mean 2.1±1.1); uterine fecundity ranged from 1 to 6 (mean 3.3±1.2). the size of the pups varied from 72 to 220 mm tl and their weight ranged between 1.6–48.5 g (mean 11.7±8.6). the spiny dogfish was compared with fish from other study areas and was found to be smaller in size in the eastern mediterranean sea, reaching maturity at smaller sizes and obtaining lower fecundity than female fish in other areas.

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