Maximum intrinsic rate of population increase in sharks, rays, and chimaeras: the importance of survival to maturity

Pardo, Sebastián A.; Kindsvater, Holly K.; Reynolds, John D.; Dulvy, Nicholas K.

doi:10.1101/051482

Cited by 26 publications

(42 citation statements)

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“…The total population of white sharks on the east coast of Australia and New Zealand was recently estimated to be 5,460 individuals, including 750 mature individuals (Bruce et al, ), suggesting the population within New Zealand waters alone met Criterion D (‘very small or restricted population’, <1,000 mature individuals). Given their naturally low population size, combined with a low estimate of maximum intrinsic rate of population increase r max (Pardo, Kindsvater, Reynolds, & Dulvy, ), and documented interactions with fisheries some continuing population decline (10% over three generations) is projected. A generation length of 39 years for this species was based on age data from Natanson and Skomal ().…”

Section: Resultsmentioning

confidence: 99%

The extinction risk of New Zealand chondrichthyans

Finucci

Duffy²,

Francis

et al. 2019

Aquatic Conservation

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1. The national extinction risk of 103 New Zealand chondrichthyans (sharks, rays, and chimaeras),~10% of the global chondrichthyan fauna, was evaluated for the first time using the International Union for Conservation of Nature Red List of Threatened Species Categories and Criteria. Across 32 families, 103 species were assessed.2. New Zealand holds a high degree of species endemism (20%) with deepwater species dominating the fauna (77%). Sharks were the most speciose group with 68 species (66%), followed by 24 rays (23%), and 11 chimaeras (10%).3. Most species were assessed as Least Concern (60%, 62 species) or Data Deficient (32%, 33 species), with four (3.8%) species listed as Near Threatened and four (3.8%) in a threatened category (Vulnerable, Endangered, Critically Endangered).Threatened species are all oceanic pelagic, of which two are only visitors to New Zealand waters, and their status the result of broader regional declines.4. These results are in stark contrast to other recent regional assessments in Europe and the Arabian Sea and adjacent areas, where up to half of species were listed in a threatened category. However, given New Zealand's extensive deepwater fishing effort and rapid collapses of deepwater chondrichthyan fisheries elsewhere, it is possible that New Zealand populations of many deepwater species are the remnants of previously reduced populations that are now at a low, yet stable level.Ongoing species-level catch monitoring will be required to ensure these species do not become threatened. Recommendations for future research and conservation efforts include resolvingtaxonomic uncertainties, understanding habitat use, and increasing regional collaborations to better understand the effects of fishing on wider-ranging species.

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Section: Resultsmentioning

confidence: 99%

The extinction risk of New Zealand chondrichthyans

Finucci

Duffy²,

Francis

et al. 2019

Aquatic Conservation

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“…This means that the above issues have the potential to extend well beyond the specific examples above. For example, age‐at‐maturity, another key determinant of population productivity (Pardo et al., ; Smith, Au, & Show, ), is frequently obtained from the inverse of a growth curve at length‐at‐maturity, meaning it too would be susceptible to biased growth parameters. Sidestepping the use of biased parameters altogether is also difficult.…”

Section: Resultsmentioning

confidence: 99%

Evidence for systemic age underestimation in shark and ray ageing studies

Harry

2017

Fish and Fisheries

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Numerous studies have now demonstrated that the most common method of ageing sharks and rays, counting growth zones on calcified structures, can underestimate true age. I reviewed bomb carbon dating (n = 15) and fluorochrome chemical marking (n = 44) age validation studies to investigate the frequency and magnitude of this phenomenon. Age was likely to have been underestimated in nine of 29 genera and 30% of the 53 populations studied, including 50% of those validated using bomb carbon dating. Length and age were strongly significant predictors of occurrence, with age typically underestimated in larger and older individuals. These characteristics suggest age underestimation is likely a systemic issue associated with the current methods and structures used for ageing. Where detected using bomb carbon dating, growth zones were reliable up to 88% of asymptotic length (L∞) and 41% of maximum age (AMax). The maximum magnitude of age underestimation, ΔMax, ranged from five to 34 years, averaging 18 years across species. Current perceptions of shark and ray life histories are informed to a large extent by growth studies that assume calcified ageing structures are valid throughout life. The widespread age underestimation documented here shows this assumption is frequently violated, with potentially important consequences for conservation and management. In addition to leading to an underestimation of longevity, the apparent loss of population age‐structure associated with it may unexpectedly bias growth and mortality parameters. Awareness of these biases is essential given shark and ray population assessments often rely exclusively on life history parameters derived from ageing studies.

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“…We use the following version of this equation to calculate r max . Unlike previous estimates of r max for chondrichthyan species [12, 29, 30], this equation accounts for juvenile mortality [31]: where l α mat is survival to maturity and is calculated as l α mat = ( e ‒ M ) α mat , b is the annual reproductive output of daughters, α mat is age at maturity in years, and M is the instantaneous natural mortality. We then solve equation 10 for r max using the function in R. To account for uncertainty in input parameters, we use a Monte Carlo approach and draw values from parameter distributions to obtain 10,000 estimates of r max .…”

Section: Methodsmentioning

confidence: 99%

“…We used this estimate of M to calculate survival to maturity l α mat as ( e ‒ M ) α mat . This method produces realistic estimates of r max when accounting for survival to maturity [31]. We also use our estimate of Z from Part 2, which represents both natural and fishing mortality, to contextualize our estimate of M .…”

Section: Methodsmentioning

confidence: 99%

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Devil in the details: growth, productivity, and extinction risk of a data-sparse devil ray

Pardo

Kindsvater

Cuevas-Zimbrón³

et al. 2016

Preprint

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1Devil rays (Mobula spp.) face rapidly intensifying shing pressure to meet the ongoing interna-2 tional trade and demand for their gill plates.is has been exacerbated by trade regulation of 3 manta ray gill plates following their 2014 CITES listing. Furthermore, the paucity of information 4 on growth, mortality, and shing e ort for devil rays make quantifying population growth rates 5 and extinction risk challenging. Here, we use a published size-at-age dataset for a large-bodied 6 devil ray species, the Spinetail Devil Ray (Mobula japanica), to estimate somatic growth rates, 7 age at maturity, maximum age and natural and shing mortality. From these estimates, we go 8 on to calculate a plausible distribution of the maximum intrinsic population growth rate (r max ) 9 and place the productivity of this large devil ray in context by comparing it to 95 other chon-10 drichthyan species. We nd evidence that larger devil rays have low somatic growth rate, lowAll rights reserved. No reuse allowed without permission.(which was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint . http://dx.doi.org/10.1101/043885 doi: bioRxiv preprint first posted online Mar. 17, 2016; annual reproductive output, and low maximum population growth rates, suggesting they have 12 low productivity. Devil ray maximum intrinsic population growth rate (r max ) is very similar to 13 that of manta rays, indicating devil rays can potentially be driven to local extinction at low levels 14 of shing mortality. We show that shing rates of a small-scale artisanal Mexican shery were 15 up to three times greater than the natural mortality rate, and twice as high as our estimate of 16 r max , and therefore unsustainable. Our approach can be applied to assess the limits of shing 17 and extinction risk of any species with indeterminate growth, even with sparse size-at-age data.

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Maximum intrinsic rate of population increase in sharks, rays, and chimaeras: the importance of survival to maturity

Cited by 26 publications

References 26 publications

The extinction risk of New Zealand chondrichthyans

The extinction risk of New Zealand chondrichthyans

Evidence for systemic age underestimation in shark and ray ageing studies

Devil in the details: growth, productivity, and extinction risk of a data-sparse devil ray

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