Impact of biology knowledge on the conservation and management of large pelagic sharks

Abstract

Population growth rate, which depends on several biological parameters, is valuable information for the conservation and management of pelagic sharks, such as blue and shortfin mako sharks. However, reported biological parameters for estimating the population growth rates of these sharks differ by sex and display large variability. To estimate the appropriate population growth rate and clarify relationships between growth rate and relevant biological parameters, we developed a two-sex age-structured matrix population model and estimated the population growth rate using combinations of biological parameters. We addressed elasticity analysis and clarified the population growth rate sensitivity. For the blue shark, the estimated median population growth rate was 0.384 with a range of minimum and maximum values of 0.195–0.533, whereas those values of the shortfin mako shark were 0.102 and 0.007–0.318, respectively. The maturity age of male sharks had the largest impact for blue sharks, whereas that of female sharks had the largest impact for shortfin mako sharks. Hypotheses for the survival process of sharks also had a large impact on the population growth rate estimation. Both shark maturity age and survival rate were based on ageing validation data, indicating the importance of validating the quality of these data for the conservation and management of large pelagic sharks.

Future Distribution of Suitable Habitat for Pelagic Sharks in Australia Under Climate Change Models

“…Many shark species are already globally threatened due to fisheries overexploitation (Queiroz et al, 2019) coupled with their low fecundity, late age at maturity, and slow growth (Cortés, 2000;Garcia et al, 2008;Yokoi et al, 2017). In fact, 16.6% of shark species are estimated to be threatened with extinction, and another 37.9% of shark species are categorized as "Data Deficient" by the International Union for Conservation of Nature (IUCN, 2020).…”

Aspects of the reproductive biology of two pelagic sharks in the eastern Atlantic Ocean

“…The management and conservation of shark species have become extremely important due to the global increase in ocean exploitations (Davis & Worm, 2013;Davidson et al, 2016;Yokoi et al, 2017). As apex predator in the marine ecosystem, sharks are vulnerable to overexploitation due to their biological characteristics.…”

“…As apex predator in the marine ecosystem, sharks are vulnerable to overexploitation due to their biological characteristics. The stock of some of these species takes much time to recover from over-exploitation due to their late sexual maturity, low fecundity and slow growth rate (Barker & Schluessel, 2005;Ferretti et al, 2010;Yokoi et al, 2017).…”

Age determination and growth of the blue shark (Prionace glauca) in the western North Pacific Ocean

“…Similar patterns also have been reported in other species, such as the blacktip shark (Carcharhinus limbatus) (Branstetter, 1987) and the shortfin mako (Isurus oxyrinchus) . Several triggers, such as environment experienced (e.g., water temperature), prey availability, physiological differences, and movement patterns, might be related to postnatal band formation (e.g., Natanson and Wells et al, 2017).…”

“…Because sexual dimorphism is common in shark species -with females being typically larger than males (Sims, 2005)-life history parameters should be based on sexspecific growth equations for proper stock assessment and management (Punt and Walker, 1998;Chang and Liu, 2009). Estimates of parameters, such as "spawning biomass" (the term spawning biomass is used in stock assessment reports to represent the biomass of reproductive organisms), maximum sustainable yield, and fishing intensity, can be strongly biased when an assessment does not take sexual dimorphism into consideration (Wang et al, 2005).…”