Eco-evolutionary dynamics of Atlantic cod spatial behavior maintained after the implementation of a marine reserve

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Sea temperature effects on depth use and habitat selection in a marine fish community

Understanding the responses of aquatic animals to temperature variability is essential to predict impacts of future climate change and to inform conservation and management. Most ectotherms such as fish are expected to adjust their behaviour to avoid extreme temperatures and minimize acute changes in body temperature. In coastal Skagerrak, Norway, sea surface temperature (SST) ranges seasonally from 0 to over 20°C, representing a challenge to the fish community which includes cold-, cool- and warm-water affinity species.publishedVersio

A longitudinal study of the biometric and refractive changes in full-term infants during the first year of life

AbstractChanges in ocular axial dimensions and refraction were followed longitudinally, using ultrasonography and retinoscopy, during the first year of life (mean ages 4–53 weeks) of a group of 20 full-term infants (10 male, 10 female). Using a mixed-model regression analysis, axial length changes as a function of time were found to be best described by a quadratic expression (AL=17.190+0.128x−0.0013x2, where AL is the axial length in mm and x is the age in weeks), while anterior chamber depth changed linearly (ACD=2.619+0.018x, where ACD is the anterior chamber depth in mm): lens thickness was essentially constant. Spherical equivalent refraction through most of the first year showed a steady reduction in hypermetropia (SER=2.982−0.032x, where SER is the spherical equivalent refraction in dioptres): astigmatism also tended to diminish. Mean hyperopic refractive errors through the year were negatively correlated with corresponding axial lengths (SER=12.583−0.541AL), but some individual subjects showed marked departures from this pattern. These results are discussed in relation to concepts of emmetropization

Personalities influence spatial responses to environmental fluctuations in wild fish

Although growing evidence supports the idea that animal personality can explain plasticity in response to changes in the social environment, it remains to be tested whether it can explain spatial responses of individuals in the face of natural environmental fluctuations. This is a major challenge in ecology and evolution as spatial dynamics link individual‐ and population‐level processes. In this study, we investigated the potential of individual personalities to predict differences in fish behaviour in the wild. Specifically, our goal was to answer if individual differences in plasticity of space use to sea surface temperature could be explained by differences in personality along the reactive–proactive axis. To address this question, we first conducted repeated standard laboratory assays (i.e., open‐field test, novel object test and mirror stimulation test) to assess the personality type of 76 wild‐caught Atlantic cod (Gadus morhua). Next, we released the fish back into the sea and monitored their spatial behaviour over large temporal (16 months) and spatial (a whole fjord) scales, using high‐resolution acoustic tracking. We demonstrate that (a) cod personality traits are structured into a proactive–reactive syndrome (proactive fish being more bold, exploratory and aggressive), (b) mean depth use of individuals is mainly driven by sea temperature and (c) personality is a significant predictor of home range changes in the wild, where reactive, but not proactive, individuals reduced their home range as sea temperature increased. These findings expand our understanding of the ecological consequences of animal personality and the mechanisms shaping spatial dynamics of animals in nature.publishedVersio

Inferring individual fate from aquatic acoustic telemetry data

Acoustic telemetry has become a popular means of obtaining individual behavioural data from a wide array of species in marine and freshwater systems. Fate information is crucial to understand important aspects of population dynamics such as mortality, predation or dispersal rates. Here we present a method to infer individual fate from acoustic telemetry arrays of receivers with overlapping detection ranges. Our method depends exclusively on information on animal movements and the characteristics and configuration of the telemetry equipment. By answering a limited number of simple questions, our method identifies six different fates: tagging mortality, natural mortality, fishing mortality, predation, dispersal and survival. Applying the method to a cod telemetry dataset, we were able to determine the fate of 97% of the individuals. We validate the results using several external sources of information, such as recaptures from fishers and control fish with known fate. The method is readily applicable to a wide array of species with minimal adjustments, expanding the range of hypotheses that can be tested using telemetry data.publishedVersio

Behavioral responses of Atlantic cod to sea temperature changes

Understanding responses of marine species to temperature variability is essential to predict impacts of future climate change in the oceans. Most ectotherms are expected to adjust their behavior to avoid extreme temperatures and minimize acute changes in body temperature. However, measuring such behavioral plasticity in the wild is challenging. Combining 4 years of telemetry-derived behavioral data on juvenile and adult (30–80 cm) Atlantic cod (Gadus morhua), and in situ ocean temperature measurements, we found a significant effect of sea temperature on cod depth use and activity level in coastal Skagerrak. During summer, cod were found in deeper waters when sea surface temperature increased. Further, this effect of temperature was stronger on larger cod. Diel vertical migration, which consists in a nighttime rise to shallow feeding habitats, was stronger among smaller cod. As surface temperature increased beyond ~15°C, their vertical migration was limited to deeper waters. In addition to larger diel vertical migrations, smaller cod were more active and travelled larger distances compared to larger specimens. Cold temperatures during winter tended, however, to reduce the magnitude of diel vertical migrations, as well as the activity level and distance moved by those smaller individuals. Our findings suggest that future and ongoing rises in sea surface temperature may increasingly deprive cod in this region from shallow feeding areas during summer, which may be detrimental for local populations of the species.Keywords: diel vertical migration, sea surface temperature, Gadus morhua, climate change, Acoustic telemetr

Restoration of Abundance and Dynamics of Coastal Fish and Lobster Within Northern Marine Protected Areas Across Two Decades

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