Using a spatially structured life cycle model to assess the influence of multiple stressors on an exploited coastal-nursery-dependent population

Abstract

Exploited coastal-nursery-dependent fish species are subject to various stressors occurring at specific stages of the life cycle: climate-driven variability in hydrography determines the success of the first eggs/larvae stages; coastal nursery habitat suitability controls juvenile growth and survival; and fisheries target mostly adults. A life cycle approach was used to quantify the relative influence of these stressors on the Eastern English Channel (EEC) population of the common sole (Solea solea), a coastal-nurserydependent flatfish population which sustains important fisheries. The common sole has a complex life cycle: after eggs hatch, larvae spend several weeks drifting in open water. Survivors go on to metamorphose into benthic fish. Juveniles spend the first two years of their life in coastal and estuarine nurseries. Close to maturation, they migrate to deeper areas, where different subpopulations supplied by different nurseries reproduce and are exploited by fisheries. A spatially structured age-and stagebased hierarchical Bayesian model integrating various aspects of ecological knowledge, data sources and expert knowledge was built to quantitatively describe this complex life cycle. The model included the low connectivity among three subpopulations in the EEC, the influence of hydrographic variability, the availability of suitable juvenile habitat and fisheries. Scenarios were designed to quantify the effects of interacting stressors on population renewal. Results emphasized the importance of coastal nursery habitat availability and quality for the population renewal. Realistic restoration scenarios of the highly degraded Seine estuary produced a two-third increase in catch potential for the adjacent subpopulation. Fisheries, however, remained the main source of population depletion. Setting fishing mortality to the maximum sustainable yield led to substantial increases in biomass (+100%) and catch (+33%) at the EEC scale. The approach also showed how climate-driven variability in hydrography is likely to interact with human pressures, e.g., overfishing increased the sensitivity to unfavorable conditions. Our results provided insights into the dynamics of numerous exploited coastal-nursery-dependent species while paving the way toward more robust advice for sustainable management of these resources.

How larval traits of six flatfish species impact connectivity

“…The quantification of the exchange by dispersal between areas represents a first step to build a full life cycle model to improve fisheries management. An example of such development is the full life cycle model of flatfish in the EEC (Archambault et al ).…”

Conflicts in the coastal zone: human impacts on commercially important fish species utilizing coastal habitat

“…In coastal marine systems, more than half of combined impacts are derived from non-additive interactions, meaning simple additive approaches are often insufficient to adequately describe or predict impacts (Teichert et al, 2016). A simple illustration of synergistic cumulative impacts is the multiplicative effect of habitat loss and the simultaneous degradation of habitat quality in residual habitats (Archambault et al, 2015). So-called positively synergistic stressors, where multiple pressures amplify the stress on species, will have the largest impact, potentially altering entire assemblages (Tomczak et al, 2013).…”

“…This is not to say that such endeavours are not warranted; to the contrary, they can act as informed thought experiments in probing ecological questions (Levin and Stunz, 2005). However, such approaches should be iterative (Rochette et al, 2013;Archambault et al, 2015Archambault et al, , 2016 and considered with an appropriate level of criticism until research in the system they aim to describe matures and provides ample and accurate parameters to inform the model (Meynecke and Richards, 2014;Archambault et al, 2016). In the short term, approaches that reduce the number of parameters in a model can provide better predictions of population changes (Ruiz et al, 2009).…”

Vulnerability and Decision-Making in Multispecies Fisheries: A Risk Assessment of Bacalao (Mycteroperca olfax) and Related Species in the Galapagos’ Handline Fishery

“…Exploitation (by fishing) is considered the main cause for these declines or extirpations, as most of the world's marine fisheries are fully exploited or overexploited [5,6]. Fishing affects fish populations through direct mortality on target species, but also through indirect effects such as by-catch, habitat destruction, functional alterations of ecosystems, and human-induced evolutionary shifts in populations [7,8]. Notwithstanding, fishing (especially small-scale) plays a vital role in health nutrition, food security, and economic development of humans, especially coastal societies [9,10].…”