Abstract:Harvest can change phenotypic traits of populations through immediate demographic 15 consequences, evolutionary responses to harvest selection, or developmental responses by 16 individuals. This study investigated the plastic phenotypic effects of harvest on size and age at 17 maturity in a commercially exploited freshwater fish. We tested an individual growth and life 18 history plasticity model using lagged correlations incorporating how harvesting of ages 2 and 19 older fish influenced the abundance of juvenile fish, resource availability, individual growth 20 rates, and carry-over responses in age and size at maturity. Our test used cohort data for Lake as expected under the plasticity model. In Lake Erie, age and size at maturity in yellow perch 25 appear to be responding to other drivers, such as harvest-induced dynamics of other fish stocks 26 or ecosystem changes that are independent of harvest. Introduction 28The prominent trends in phenotypic traits observed in exploited populations suggest the 29 effects of harvest can extend beyond demographic changes in population size, age structure and 30 sex ratio (Jørgensen et al. 2007; Anderson et al. 2008; Sharpe and Hendry 2009). demographic phenotypic effects of harvest are concerning because any effects on age and length 32 at maturity can result in losses of biodiversity, reduced productivity and economic value (Eikeset 33 et al. 2013), and increased risk of population collapse (Hard et al. 2008; Kuparinen et al. 2011; 34 Pinsky and Palumbi 2014). Harvest can cause phenotypic change through three processes:35 phenotypic selection within a generation resulting from gear selectivity, evolutionary responses 36 over multiple generations to phenotypic selection acting on heritable phenotypic variation, and 37 plastic growth rate responses and subsequent changes in maturation (Rochet 1998). 38Distinguishing among these processes is important because evolutionary changes in phenotypes 39 may be more difficult to reverse than plastic changes when harvest is relaxed (Conover et al. 44Changes in the growth rate of immature individuals can be a proximal cause of 45 maturation plasticity in many fishes (Alm 1959; Engelhard and Heino 2004; Enberg et al. 2012). 46 We assume that in the face of energy limits, maturation age and size trade off against immature 47 growth rate so that faster growing juveniles mature earlier and at smaller size than slower 52The scope for smaller adult body size in fish is high because size at maturity is approximately 53 two thirds of asymptotic size and earlier maturation at smaller size leads to smaller size at later 54 ages when adult growth rate is reduced following maturation (Charnov and Berrigan 1990). 55Plasticity in maturation and adult size may be expressed in many fishes when immature growth 56 rate responds to changes in resource availability. Density-dependent population regulation can strongly affect life history dynamics in 69 freshwater fish populations, including Great Lake stocks of yellow ...

World-wide, many burbot Lota lota (L.) populations have been extirpated or are otherwise in need of conservation measures. By contrast, burbot made a dramatic recovery in Lake Erie during 1993-2001 but declined during 2002-2007, due in part to a sharp decrease in recruitment. We used Akaike's Information Criterion to evaluate 129 linear regression models that included all combinations of one to seven ecological indices as predictors of burbot recruitment. Two models were substantially supported by the data: (i) the number of days in which water temperatures were within optimal ranges for burbot spawning and development combined with biomass of yearling and older (YAO) yellow perch Perca flavescens (Mitchill); and (ii) biomass of YAO yellow perch. Warmer winter water temperatures and increases in yellow perch biomass were associated with decreases in burbot recruitment. Continued warm winter water temperatures could result in declines in burbot recruitment, particularly in the southern part of the species' range.

We used GIS mapping techniques to examine capture data for Burbot Lota lota from annual gill-net surveys in Canadian waters of Lake Erie during late August and September 1994-2011. Adult males were captured over a larger area (3-17% for ≥20% maximum yearly catch [MYC]) than adult females. More males than females were caught in the gill nets in 14 of the 15 study years. Collectively, these results support a hypothesis of greater activity by adult males during summer, when Burbot are actively feeding. The area of capture contracted by more than 60% (for ≥20% MYC) for both sexes during the time period, which is consistent with the documented decrease of the Burbot population in the lake. The sex ratio (females : males) varied over the time series but declined steadily from 0.97 in 2001 to 0.59 in 2011. The overlap in the capture areas of adult males and females was scale dependent. The depth distribution at which adult Burbot were caught did not change over the time series, and there was no difference in the median depths (about 30 m) at which adult male and female Burbot were caught. The last results are consistent with the Burbot's reliance on coldwater habitats. Additional research is recommended, including telemetry to describe daily and seasonal movements and assessment of gender bias in active and passive capture gear.

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