Demographic plasticity facilitates ecological and economic resilience in a commercially important reef fish

Abstract

1. Variation in life-history characteristics is evident within and across animal populations. Such variation is mediated by environmental gradients and reflects metabolic constraints or trade-offs that enhance reproductive outputs. While generalizations of life-history relationships across species provide a framework for predicting vulnerability to overexploitation, deciphering patterns of intraspecific variation may also enable recognition of peculiar features of populations that facilitate ecological resilience.2. This study combines age-based biological data from geographically disparate populations of bluespine unicornfish (Naso unicornis)-the most commercially valuable reef-associated species in the insular Indo-Pacific-to explore the magnitude and drivers of variation in life span and examine the mechanisms enabling peculiar mortality schedules.3. Longevity and mortality schedules were investigated across eleven locations encompassing a range of latitudes and exploitation levels. The presence of different growth types was examined using back-calculated growth histories from otoliths.Growth-type-dependent mortality (mortality rates associated with particular growth trajectories) was corroborated using population models that incorporated size-dependent competition. 4. We found a threefold geographic variation in life span that was strongly linked to temperature, but not to anthropogenic pressure or ocean productivity. All populations consistently displayed a two-phase mortality schedule, with higher than expected natural mortality rates in earlier stages of post-settlement life.Reconstructed growth histories and population models demonstrated that variable growth types within populations can yield this peculiar biphasic mortality schedule, where fast growers enjoy early reproductive outputs at the expense of greater mortality, and benefits for slow growers derive from extended reproductive outputs over a greater number of annual cycles. This promotes population | 1889Journal of Animal Ecology TAYLOR eT AL.

Demography of the largest and most endangered Brazilian parrotfish, Scarus trispinosus, reveals overfishing

“…Maximum sizes and ages at lower latitudes are expected to be lower, since age-based demography of reef fishes varies with sea temperature (e.g. Choat et al 2003, Robertson et al 2005, Taylor & Pardee 2017, Taylor et al 2019. Despite potential differences in longevity between individuals in our study area and in the Abrolhos Bank, age and size of maturation were comparable between these regions (Table 1).…”

Comparative demography of commercially important species of coral grouper, Plectropomus leopardus and P. laevis, from Australia's great barrier reef and Coral Sea marine parks

“…given that historical collections were made on hook and line (Heupel et al, 2010;Mapstone et al, 2004) Differences in environment and habitat often manifest as changes in lifetime growth (Choat & Robertson, 2002;Mora, 2015;Taylor et al, 2019), but growth profiles and length-at-age estimates for P. leopardus and P. laevis were similar between regions. Stable isotope (Hempson et al, 2017;Matley et al, 2017) and stomach content (Kingsford, 1992) analyses have demonstrated that coral grouper are capable of feeding on a range of prey items and may modify their diet following local disturbances (Wen et al, 2016).…”

“…However, we emphasize caution when comparing growth parameters among models when sizes at settlement were not constrained to a common value. Broad spatial studies that span large environmental gradients ( e.g ., Trip et al ., 2008) or the application of biochronology techniques ( e.g ., Taylor et al ., 2019) may further improve the resolution of environmental‐driven variation in growth of coral grouper.…”

“…Coral reef fishes can show remarkable plasticity in their life history in response to anthropogenic pressures ( e.g ., fishing; Rochet, 1998) or environmental variation ( e.g ., temperature; Choat & Robertson, 2002; Mora, 2015; Taylor et al ., 2019). Understanding the factors that influence demographic traits like lifetime growth and mortality are essential for developing population or species‐specific management strategies, assessing the efficacy of existing regulations and predicting how changing disturbance or fishing regimes might influence population dynamics (Brown et al ., 2012; Pratchett et al ., 2018; Wilson et al ., 2008).…”

Growth impacts in a changing ocean: insights from two coral reef fishes in an extreme environment

“…While numerous studies have examined the implications of increasing temperature and temperature variability on coral reef fish growth (e.g. Munday et al 2008;Messmer et al 2017;Taylor et al 2019), to our knowledge there has been no investigation of the combined effect of increasing temperature and salinity on coral reef fish demography. This is despite the evidence of synergism between the two stressors (Claireaux and Lagarde 1999;Jian et al 2003) and the likely occurrence of both stressors in already dry regions and hyper-saline (sensu saltier than ocean salinity) semienclosed seas in the near future (such as the Arabian Gulf, Red Sea and Mediterranean Sea) (Durack et al 2012;Skliris et al 2014;Zika et al 2018).…”