Unconfounding the effects of climate and density dependence using 60 years of data on spiny dogfish (Squalus acanthias)

2009 ◽  
Vol 66 (3) ◽  
pp. 351-366 ◽  
Author(s):  
Ian G. Taylor ◽  
Vincent F. Gallucci
Keyword(s):  
Population Growth Rate ◽  
Growth Parameters ◽  
Squalus Acanthias ◽  
Matrix Analysis ◽  
Leslie Matrix ◽  
Demographic Parameters ◽  
Spiny Dogfish ◽  
Northeast Pacific ◽  
Demographic Traits ◽  
Rapid Environmental Change

The confounded effects of changes in climate and density on a population’s demography are hard to separate for long-lived species because demographic traits are usually the aggregated result of conditions faced over years. Demographic parameters are compared for spiny dogfish ( Squalus acanthias ) in the Northeast Pacific, the longest lived and latest maturing of all sharks, using samples from the 1940s and 2000s. This 60-year interval has seen ocean temperatures rise by almost 1 °C and dogfish harvests peak above 50 000 tonnes (t)·annum–1 and then drop below 50 t·annum–1. Over this period, the age at 50% maturity for dogfish declined from 43 to 32 years, while the estimated average number of embryos per litter for a 100 cm dogfish increased from 5.9 to 6.7. Growth parameters changed significantly, with faster growth to a smaller size. Leslie matrix analysis showed that these changes could lead to an increase in population growth rate of about 1%. Comparison with published demographic parameters from the 1970s and 1980s indicated that the greatest change in demographic parameters occurred between the 1940s and 1970s, prior to the largest changes in ocean temperatures. The implications for fishing on long-lived populations during times of rapid environmental change are explored.

Diagnosing declining grassland wader populations using simple matrix models

2009 ◽  
Vol 59 (1) ◽  
pp. 127-144 ◽  
Author(s):  
Lia Hemerik ◽  
Chris Klok ◽  
Maja Roodbergen
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Matrix Models ◽  
Population Growth Rate ◽  
Adult Stage ◽  
Demographic Data ◽  
Leslie Matrix ◽  
Adult Survival ◽  
Demographic Parameters ◽  
Survival And Reproduction

AbstractMany populations of wader species have shown a strong decline in number in Western-Europe in recent years. The use of simple population models such as matrix models can contribute to conserve these populations by identifying the most profitable management measures. Parameterization of such models is often hampered by the availability of demographic data (survival and reproduction). In particular, data on survival in the pre-adult (immature) stage of wader species that remain in wintering areas outside Europe are notoriously difficult to obtain, and are therefore virtually absent in the literature. To diagnose population decline in the wader species; Black-tailed Godwit, Curlew, Lapwing, Oystercatcher, and Redshank, we extended an existing modelling framework in which incomplete demographic data can be analysed, developed for species with a pre-adult stage of one year. The framework is based on a Leslie matrix model with three parameters: yearly reproduction (number of fledglings per pair), yearly pre-adult (immature) and yearly adult (mature) survival. The yearly population growth rate of these populations and the relative sensitivity of this rate to changes in survival and reproduction parameters (the elasticity) were calculated numerically and, if possible, analytically. The results showed a decrease in dependence on reproduction and an increase in pre-adult survival of the population growth rate with an increase in the duration of the pre-adult stage. In general, adult survival had the highest elasticity, but elasticity of pre-adult survival increased with time to first reproduction, a result not reported earlier. Model results showed that adult survival and reproduction estimates reported for populations of Redshank and Curlew were too low to maintain viable populations. Based on the elasticity patterns and the scope for increase in actual demographic parameters we inferred that conservation of the Redshank and both Curlew populations should focus on reproduction. For one Oystercatcher and the Black-tailed Godwit populations we suggested a focus on both reproduction and pre-adult survival. For the second Oystercatcher population pre-adult survival seemed the most promising target for conservation. And for the Lapwing populations all demographic parameters should be considered.

scholarly journals Life-history traits of the spiny dogfish Squalus acanthias in the Adriatic Sea

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Giada Bargione ◽  
Fortunata Donato ◽  
Mario La Mesa ◽  
Carlotta Mazzoldi ◽  
Emilio Riginella ◽  
...  
Keyword(s):  
Life History ◽  
Life History Traits ◽  
Adriatic Sea ◽  
Growth Parameters ◽  
Sampling Period ◽  
Squalus Acanthias ◽  
Spiny Dogfish ◽  
The North ◽  
Size At Sexual Maturity ◽  
The Individual

Abstract Pivotal life history traits concerning age structure and reproduction of the spiny dogfish (Squalus acanthias, Linnaeus 1758) were investigated in the Adriatic Sea from mid February 2012 to mid July 2013 and in 2016. The whole sample consisted of 176 females and 150 males, ranging between 217–1025 mm and 219–875 mm, respectively. The individual age, which was estimated using a cross-sectioning technique of the second dorsal-fin spine, ranged from 0 to 13+ years for females and from 0 to 9+ years for males. Based on the length-at-age estimates, the Gompertz growth parameters were L∞ = 1130 mm, k = 0.18 and L∞ = 920 mm, k = 0.24 for females and males, respectively. The size at sexual maturity (L50) was 659 mm for females and 575 mm for males, corresponding to 7.5 and 5.5 years of age (A50), respectively. Mean biennial fecundity was approximately 11 embryos/female and 12 ripe oocytes/female. Mature males occurred during much of the sampling period, while mature females with nearly full-term embryos were exclusively recorded in May 2013 and July 2016. Monitoring of catches conducted in a sample port of the north Adriatic (Chioggia) over the past 20 years has shown fluctuating trends in landings, with peaks during the summer reproductive season.

Metabolic Rate and Energy Expenditure of the Spiny Dogfish, Squalus acanthias

1978 ◽  
Vol 35 (6) ◽  
pp. 816-821 ◽  
Author(s):  
J. R. Brett ◽  
J. M. Blackburn
Keyword(s):  
Energy Expenditure ◽  
Metabolic Rate ◽  
Key Words ◽  
Swimming Performance ◽  
Squalus Acanthias ◽  
Spiny Dogfish ◽  
Metabolic Rates ◽  
Performance Curve ◽  
Power Performance ◽  
General Energy

The metabolic rate of spiny dogfish, Squalus acanthias, was determined in both a tunnel respirometer and a large, covered, circular tank (mass respirometer). Swimming performance was very poor in the respirometer, so that a power–performance curve could not be established. Instead, resting metabolic rates were determined, with higher rates induced by causing heavy thrashing (active metabolism). Routine metabolic rates were measured for the spontaneous activity characterizing behavior in the circular tank. For fish of 2 kg mean weight, the metabolic rates at 10 °C were 32.4 ± 2.6 SE (resting), 49.2 ± 5.0 SE (routine), and 88.4 ± 4.6 SE (active) mg O2∙kg−1∙h−1. Assuming that the routine rate represents a general energy expenditure in nature, this is equivalent to metabolizing about 3.8 kcal∙kg−1∙d−1 (15.9 × 103 J∙kg−1∙d−1). Key words: dogfish, metabolic rates, energetics, respiration

scholarly journals Bounds on Biomass Estimates and Energetic Consequences of Ctenophora in the Northeast U.S. Shelf Ecosystem

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Michael D. Ford ◽  
Jason S. Link
Keyword(s):  
Feeding Strategy ◽  
Marine Ecosystem ◽  
High Energy ◽  
Gelatinous Zooplankton ◽  
Squalus Acanthias ◽  
High Energy Density ◽  
Spiny Dogfish ◽  
Sampling Device ◽  
Large Marine Ecosystem ◽  
Major Increase

Previous descriptions have noted that the stomach samples of spiny dogfish, Squalus acanthias, showed a major increase in the overall occurrence and hence implied abundance of Ctenophora. This apparent and persistent gelatinous zooplankton outbreak is increasingly more common in the world’s oceans. We briefly explore the energetic ramifications of ctenophores in the spiny dogfish diet, inferring that the presence of gelatinous zooplankton represents an ambient feeding strategy. Relative to other prey, ctenophores are not a high energy density prey item. However, given varying assumptions of the amount of ctenophores consumed, they may be an important staple in the diet of spiny dogfish. We also examine the utility of using spiny dogfish as a gelatinous zooplankton sampling device. Using five calculation methodologies, we provide bounds on potential abundance and biomass estimates of ctenophores in the Northeast U.S. shelf ecosystem. We then contextualize these findings relative to the implications for the Northeast U.S. and any large marine ecosystem.

Biology and Management of Dogfish Sharks

2009 ◽  
Keyword(s):  
Life History ◽  
Pacific Coast ◽  
Puget Sound ◽  
Squalus Acanthias ◽  
Spiny Dogfish ◽  
Dietary Analysis ◽  
Strait Of Georgia ◽  
Food Items ◽  
Abundance Estimates ◽  
Commercial Species

Abstract.—Spiny dogfish <em>Squalus acanthias </em>have been an important commercial species on Canada’s Pacific coast for more than 130 years. In this study we show that the spiny dogfish life history results in juveniles remaining in pelagic waters for 10–15 years after birth, with lengths up to about 60 cm. Abundance estimates show that the numbers of these young dogfish, as well as some older dogfish in the pelagic waters, appear to represent a relatively large percentage of the population in these two regions. Dietary analysis shows that while euphausiids and teleosts constitute the major food items, regardless of size/age, dogfish feed on a number of species within the ecosystem. After about 15 years, there is a movement into demersal habitats where individuals eventually mature. Because dogfish are long lived, and because they are found throughout the pelagic zone and demersal habitats, it is probable that they play a key role in the Strait of Georgia and Puget Sound ecosystems.

Sign in / Sign up

Export Citation Format

Share Document