Multiple growth-correlated life history traits estimated simultaneously in individuals

When gene flow is limited and harvesting is intensive, fishing may alter life histories and favour trait combinations that collectively reduce adult body size. However, empirical evidence of downsizing of adults in small-bodied coastal fish is still scarce, in part due to the lack of knowledge about the selective nature of certain fishing gears, such as recreational angling, and the difficulties in estimating the dispersion of pelagic early-life stages. Using the small-bodied sedentary coastal marine fish Serranus scriba as a model, we first empirically show that recreational angling selects for life-history traits (i.e. increased reproductive investment) that promote downsizing of adults. Second, using Lagrangian particle dispersion modelling, we show how local hydrodynamics generates patterns of limited connectivity and the emergence of meta-population structure. Finally, the life histories presently observed in isolated populations of S. scriba that experienced differential fishing pressure matched expectations of fishing-induced downsizing of adult body size. Body size is an important trait in aquatic food webs, and evolutionary downsizing might have unforeseen consequences. From a precautionary perspective, maintaining the metapopulation structure and the full range of genotypes inherent in them is important, even for smallbodied, geographically restricted fish species that are mainly harvested by recreational anglers.

Section: Discussionmentioning

confidence: 99%

Section: Estimation Of Individual Life-history Traits Of Serranus Scribamentioning

confidence: 99%

Selective exploitation of spatially structured coastal fish populations by recreational anglers may lead to evolutionary downsizing of adults

Alós¹,

Palmer²,

Catalán³

et al. 2014

“…With specific reference to estimating the onset of maturity, Rijnsdorp & Storbeck (1995) applied the segmented regression approach to back-calculated growth data from otolith measurements of North Sea plaice Pleuronectes platessa, and, more recently, Baulier & Heino (2008) investigated its application to growth patterns in Atlantic herring Clupea harengus, although neither 148 Scott & Heikkonen: Estimating age at first maturity in plaice study found the approach to be entirely satisfactory, recommending instead that a bio-energetic modelling approach may provide better estimates. Mollet et al (2010) extended the method to estimate multiple life-history parameters using the segmented regression approach to fit an energy allocation model to individual growth trajectories for female North Sea plaice. Their method provided estimates of the age of the onset of maturation that corresponded well with those obtained from direct observation.…”

Section: Resale or Republication Not Permitted Without Written Consenmentioning

confidence: 99%

“…Lester et al (2004) found the von Bertalanffy equation to be an appropriate model for post-maturity somatic growth but not appropriate for pre-maturation growth, and it is argued that multi-phase models may provide a more appropriate representation of growth in fishes (Dumas et al 2007, Quince et al 2008. These findings support the further investigation of alternative growth assumptions when investigating trends in maturation schedules, and the approach of Mollet et al (2010) has already begun this process through the incorporation of a bio-energetic approach to energy allocation.Bio-energetic considerations alone, however, may not be sufficient to fully explain the differences between the sexes or the trends observed over time. The sexual dimorphism in growth cannot be fully explained by differences between the sexes in reproductive investment and the onset of sexual maturity (Rijnsdorp & Ibelings 1989).…”

mentioning

confidence: 98%

Estimating age at first maturity in fish from change-points in growth rate

Rd¹,

Heikkonen²

2012

Recent studies have drawn attention to the potential for evolutionary changes in lifehistory traits as a consequence of the size-selective process of fishing, and evidence of so-called fisheries-induced evolution has been reported for a number of different species. Most studies of fisheries-induced evolution have focused on changes in sexual maturation using the probabilistic maturation reaction norm method, which requires specific information on the age at which maturation occurs, often derived from macroscopic examination of the gonads. In the absence of sufficiently detailed measurements of maturity it is necessary to derive estimates of the age at which maturation occurs from alternative sources of information, for example, from length at age data. We apply a relatively simple segmented regression model to length at age data for plaice Pleuronectes platessa in the Irish Sea in order to identify the change-point between 2 specific growth schedules that can be used as a proxy for age at first maturity in individual cohorts. We use a Bayesian approach for model fitting and map the resulting distribution of change-points using Gaussian mixture models to show that the age at which the change-point occurred in individual cohorts of both male and female plaice in the Irish Sea has declined progressively over an 18 yr period between 1988 and 2005.KEY WORDS: Plaice · Maturation · Segmented regression · Reaction norm · Genetic adaptation · Phenotypic plasticity 450: 147-157, 2012 ated with reproduction, such as (1) competition for resources required for reproduction, e.g. competition for mates or nest sites; (2) the amount of space within the body cavity that can be allocated to reproductive organs; and (3) the costs of locomotion. In all 3 instances, individuals that become reproductive at a larger size might be expected to have a reduced sizespecific cost of reproduction. A life-history strategy of delayed maturation allowing for increased growth might therefore be considered optimal in terms of maximising reproductive potential, but this must be offset against competing processes such as the predation risk of foraging that might favour an alternative strategy of reduced growth and earlier maturation (Mangel & Stamps 2001). A trade-off therefore exists in the adoption of specific life-history traits that maximise reproductive potential given the competing objectives of increased growth, reduced mortality and reproductive investment. The age at which first maturity occurs is a reflection of the strategic approach that a given species takes to this trade-off and will be highly correlated with other life-history traits, such as growth rate and maximum size. Resale or republication not permitted without written consent of the publisherMar Ecol Prog SerA number of recent studies have drawn attention to the potential for evolutionary changes in life-history traits as a consequence of the size-selective process of fishing (Rijnsdorp 1993, Law 2000, Heino et al. 2002a, and evidence of so-called fisheries-induce...

“…It has been shown that past individual growth history influences maturation probability independently from age and size, with most recent growth condition (just before the age at which probability of maturing is calculated) being the most determinant factor (Morita & Fukuwaka 2006). Individual growth trajectories can be back-calculated from scale or otolith reading (Engelhard et al 2003, Baulier & Heino 2008, Mollet et al 2010), but again this information was not available.…”

Section: The Pmrn Approachmentioning

confidence: 99%

Temporal trends in age and size at maturation of four North Sea gadid species: cod, haddock, whiting and Norway pout

Marty¹,

Rochet²,

Ernande³

2014

Younger ages and smaller sizes at maturation have been observed in commercial fish stocks over the last century. We establish that age and length at 50% proportion mature (i.e. the proportion of mature individuals in a population or the probability that an individual is mature) decreased from the 1970s to the 2000s in North Sea cod Gadus morhua, haddock Melanogrammus aeglefinus and whiting Merlangius merlangus, but not in Norway pout Trisopterus esmarkii. The potential contributions of demography, phenotypic plasticity and evolution to these trends were assessed. First, maturation trends were extricated from demographic effects and growth-dependent plasticity by estimating probabilistic maturation reaction norms (PMRNs). PMRN midpoints have significantly shifted downwards at most ages for cod, haddock and whiting, but not for Norway pout. Second, increased temperature and food abundance, loosened trophic competition and relaxed social pressure may also trigger growth-independent plasticity in maturation. Principal component regression of PMRN midpoints on annual estimates of relevant environmental variables exhibiting a temporal trend suggest that, despite some evidence of environmental effects, PMRN trends were mostly independent of growth-independent plasticity in haddock, whiting and male cod, but not in female cod. According to these findings, evolution of maturation, potentially in response to fishing, is plausible in haddock, whiting and male cod, but unlikely for Norway pout, and does not explain trends in female cod maturation. In agreement with life-history theory, the maturation response was larger in fast-growing, late-and large-maturing species exhibiting moderate reproductive effort.