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Movement may critically influence population persistence in the face of disturbance. However, data on individual movements into and out of refugia in response to disturbance remain limited, leading to an incomplete understanding of the ecological significance of mobility. Using individually marked chubs Squalius torgalensis in a seasonally drying Mediterranean stream, we quantified the rate, direction and magnitude of movements out of dry season pools, and of movements displayed across the stream over the period of hydrological connection. Recapture rate was lower in individuals marked in dry season pools (3.3%; n = 894) than in individuals marked during hydrological connection (13.0%; n = 522). Nearly half the recaptures (46.7%; n = 30) of chubs marked in dry season pools corresponded to movements that were generally longer than 100 m, overpassing the average distance among isolated pools. The frequency and distances travelled out of dry season pools were similar in upstream and downstream directions. Only 20.6% of recaptures of individuals marked during hydrological connection corresponded to movements, with more frequent and larger movements in the upstream direction. Body size was related to movement probability only for chubs marked during hydrological connection. Our results highlight considerable individual variability in movement and underscore the importance of understanding the consequences of this variation and how it may be maintained in fish populations facing increasing fragmentation and intermittency of riverscapes. Copyright © 2014 John Wiley & Sons, Ltd.

Factors shaping individual behavior remain poorly understood for European cyprinids. We examined the effects of extrinsic (temperature and year) and intrinsic factors (body size and shoal size) on the daily activity of chub Squalius torgalensis, a critically endangered cyprinid found in the Torgal stream, Portugal. We quantified chub behaviors while snorkeling, using instantaneous sampling of focal individuals, in spring 2009 and 2010. We used Principal Component Analysis to describe individual behavior and assessed competing models relating individual behavior to explanatory variables using Akaike's Information Criterion. Year had a strong influence on chub behavior, with individuals spending more time drift foraging and orienting in 2009, whereas in 2010 they spent more time benthic foraging and cruising. Shoal size did not influence behaviors in 2009, but in 2010 individuals in small shoals foraged benthically and searched with greater frequency than those in large shoals. Individuals increased cruising and decreased searching as they grew in length, but the opposite trend was observed as temperature increased. Our results indicate that both extrinsic and intrinsic factors influence daily activity of chub, with individual behaviors varying between years, and depending upon shoal size, body size and temperature. This suggests that chub display high levels of individual behavioral flexibility, which may be important for fish inhabiting harsh and highly variable Mediterranean streams. Conservation efforts for this species will benefi tb y integrating behavioral information into management strategies.

Chub Squalius torgalensis and nase Chondrostoma lusitanicum, in a Mediterranean stream, showed important differences in life-history traits and population dynamics. Both species reached mean maturity at age 2 years. Chub lived up to age 5 years, spawned in March to June, grew at a maximum rate of 0.59 mm mm -1 year -1 and showed a low reproductive allocation, with fecundity and egg size increasing with body size. Nase lived up to age 4 years, spawned in January to April, grew at a maximum rate of 0.46 mm mm -1 year -1 and showed a high reproductive allocation, with egg size independent of body size. Both chub and nase showed moderate fluctuations in population size during 1991-1998, but differed in factors driving density at age. Density of age 1 year juvenile chub decreased following severe summer droughts and proportionate survival prevailed thereafter. Density of age 2 year adult nase decreased following severe spring floods, but neither environmental nor parental stock effects were detected for juveniles and older fishes. The results illustrated the interplay between life history and environmental variability in driving fish population dynamics, with impacts of both summer droughts and spring floods being contingent on species-specific patterns of spawning and reproductive investment.