Fishing‐induced evolution of growth: concepts,mechanisms and the empirical evidence

The interest in fishing‐induced life‐history evolution has been growing in the last decade, in part because of the increasing number of studies suggesting evolutionary changes in life‐history traits, and the potential ecological and economic consequences these changes may have. Among the traits that could evolve in response to fishing, growth has lately received attention. However, critical reading of the literature on growth evolution in fish reveals conceptual confusion about the nature of ‘growth’ itself as an evolving trait, and about the different ways fishing can affect growth and size‐at‐age of fish, both on ecological and on evolutionary time‐scales. It is important to separate the advantages of being big and the costs of growing to a large size, particularly when studying life‐history evolution. In this review, we explore the selection pressures on growth and the resultant evolution of growth from a mechanistic viewpoint. We define important concepts and outline the processes that must be accounted for before observed phenotypic changes can be ascribed to growth evolution. When listing traits that could be traded‐off with growth rate, we group the mechanisms into those affecting resource acquisition and those governing resource allocation. We summarize potential effects of fishing on traits related to growth and discuss methods for detecting evolution of growth. We also challenge the prevailing expectation that fishing‐induced evolution should always lead to slower growth.     

Liver histopathology in Baltic flounder (Platichthys flesus) as indicator of biological effects of contaminants

Results are presented of a study on liver histopathology in Baltic flounder (Platichthys flesus) carried out in 2001 and 2002 in four coastal sampling areas of the Baltic Sea: Kv?d?fj?rden (Swedish east coast, reference area), Klaipeda-Butinge (Lithuanian coast), Gulf of Gdansk (Polish coast), and Wismar Bay (German coast) within the framework of the EU-funded BEEP project. Liver lesions were diagnosed and categorised using standardised methodologies and, for a spatial and temporal assessment of the prevalence and types of lesions detected, a scoring system was applied, involving the calculation of mean histopathology lesion scores. 83.0% of the 436 female flounder examined (size range: 20-43 cm total length, age range: 2-8 years) were affected by liver lesions, out of which 74.3% were assigned to the category of non-specific, 3.4% to the category of early toxicopathic non-neoplastic, 4.6% to the category of pre-neoplastic and 0.7% to the category of neoplastic lesions. Mean lesions scores were highest in the areas at the Lithuanian and Swedish coast and there is indication of an impact of the age structure of the flounder populations studied, the sampling season as well as of contaminant effects.     

Late Quaternary carbonate sedimentation at the Sierra Leone Rise (eastern equatorial Atlantic Ocean)

In the eastern equatorial Atlantic Ocean, changes in the concentration of carbonate in Late Quaternary sediments resulted from reduced production of carbonate in surface waters and increased dilution with non-carbonate sediments during glacial maxima. During glacial stages, production of carbonate in surface water (measured as its accumulation rate in shallow, undissolved cores) decreased by one half. The glacial accumulation rate of non-carbonate components increased 1.5 to 4 times over Holocene values; the greatest increases occurred in the deepest cores.

Carbonate dissolution during stages 2, 3 and 4 increased the proportion of foraminiferal fragments and decreased the accumulation rate of susceptible species in the deep sites. In shallow sites, slightly increased dissolution can be detected during stage 3 while greatly increased dissolution occurred during stage 4. Bathymetric profiles of foraminiferal fragmentation and accumulation document a shoaling of the foraminiferal lysocline by 1000 m during glacial isotopic stages. We present a mass balance model of sediment accumulation for carbonate and insoluble components and from this model we estimate the rate of downslope transport and dissolution of carbonate at the Sierra Leone Rise. Our results show that during stage 4 the rate of carbonate loss to dissolution was greater than the rate observed today or during other interglacial stages. The calculated rates of dissolution for stages 2 and 3 are not significantly different from those calculated for stage 1.     

Die offenen sternhaufen M36, M38 und NGC 2477

The open star clusters M36, M38 and NGC 2477 were investigated by the strip method on charts of photographs taken with the Schmidt-Spiegel of the German Observatory Hoher List (M36/38) and the Curtis-Schmidt Telescope of the Cerro Tololo Interamerican Observatory (NGC 2477). The results are — Masses: 830, 2350, 4400 ; radii: 6.4, 10.0, 10.0 pc; central densities: 9.9, 15.3, 32.5 pc^–3; density laws: Gaussian (M36), generalized law of Schuster withn=3.00, 2.79; mean velocities of the stars 0.74, 1.01, 1.38 km s^–1.

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Mitteilungen Serie A.     

Climate projections over CORDEX Africa domain using the fifth-generation Canadian Regional Climate Model (CRCM5)

Following the CORDEX experimental protocol, climate simulations and climate-change projections for Africa were made with the new fifth-generation Canadian Regional Climate Model (CRCM5). The model was driven by two Global Climate Models (GCMs), one developed by the Max-Planck-Institut für Meteorologie and the other by the Canadian Centre for Climate Modelling and Analysis, for the period 1950–2100 under the RCP4.5 emission scenario. The performance of the CRCM5 simulations for current climate is discussed first and compared also with a reanalysis-driven CRCM5 simulation. It is shown that errors in lateral boundary conditions and sea-surface temperature from the GCMs have deleterious consequences on the skill of the CRCM5 at reproducing specific regional climate features such as the West African Monsoon and the annual cycle of precipitation. For other aspects of the African climate however the regional model is able to add value compared to the simulations of the driving GCMs. Climate-change projections for periods until the end of this century are also analysed. All models project a warming throughout the twenty-first century, although the details of the climate changes differ notably between model projections, especially for precipitation changes. It is shown that the climate changes projected by CRCM5 often differ noticeably from those of the driving GCMs.     

Carbon isotopic changes in benthic foraminifera from the western South Atlantic: Reconstruction of glacial abyssal circulation patterns

Oxygen- and carbon-isotopic analyses have been performed on the benthic foraminifer Planulina wuellerstorfi in seven Late Quaternary cores from the Vema Channel-Rio Grande Rise region. The cores are distributed over the water-depth interval of 2340 to 3939 m, which includes the present transition from North Atlantic Deep Water (NADW) to Antarctic Bottom Water (AABW).The carbon-isotopic records in the cores vary as a function of water depth. The shallowest and deepest cores show no significant glacial-interglacial difference in δ¹³C. Four of the five cores presently located in the NADW have benthic foraminiferal δ¹³C that is lower during glacial isotopic stages. Based on bathymetric gradients in δ¹³C, we conclude that, like today, there were two water masses present in the Vema Channel during glacial intervals: a water mass enriched in ¹³C overlying another water mass depleted in ¹³C. The largest gradient of change of δ¹³C with depth, however, occurred at 2.7 km, ～ 1 km shallower than the present position of this gradient.On the basis of paleontologic and sedimentologic evidence, we consider it unlikely that the NADW:AABW transition shallowed to this level. Reduced carbon-isotopic gradients between the deep basins of the North Atlantic and Pacific Oceans during the last glaciation suggest that production of NADW was reduced. Lower production of NADW may have modified the local abyssal circulation pattern in the Vema Channel region.     

Acceleration technique for Milankovitch type forcing in a coupled atmosphere-ocean circulation model: method and application for the Holocene

A method is introduced which allows the calculation of long-term climate trends within the framework of a coupled atmosphere-ocean circulation model. The change in the seasonal cycle of incident solar radiation induced by varying orbital parameters has been accelerated by factors of 10 and 100 in order to allow transient simulations over the period from the mid-Holocene until today, covering the last 7,000 years. In contrast to conventional time-slice experiments, this approach is not restricted to equilibrium simulations and is capable to utilise all available data for validation. We find that opposing Holocene climate trends in tropics and extra-tropics are a robust feature in our experiments. Results from the transient simulations of the mid-Holocene climate at 6,000 years before present show considerable differences to atmosphere-alone model simulations, in particular at high latitudes, attributed to atmosphere-ocean-sea ice effects. The simulations were extended for the time period 1800–2000 AD, where, in contrast to the Holocene climate, increased concentrations of greenhouse gases in the atmosphere provide for the strongest driving mechanism. The experiments reveal that a Northern Hemisphere cooling trend over the Holocene is completely cancelled by the warming trend during the last century, which brings the recent global warming into a long-term context.     

The Project for Intercomparison of Land-surface Parameterization Schemes (PILPS) phase 2(c) Red-Arkansas River basin experiment:: 2. Spatial and temporal analysis of energy fluxes

The energy components of sixteen Soil-Vegetation Atmospheric Transfer (SVAT) schemes were analyzed and intercompared using 10 years of surface meteorological and radiative forcing data from the Red-Arkansas River basin in the Southern Great Plains of the United States. Comparisons of simulated surface energy fluxes among models showed that the net radiation and surface temperature generally had the best agreement among the schemes. On an average (annual and monthly) basis, the estimated latent heat fluxes agreed (to within approximate estimation errors) with the latent heat fluxes derived from a radiosonde-based atmospheric budget method for slightly more than half of the schemes. The sensible heat fluxes had larger differences among the schemes than did the latent heat fluxes, and the model-simulated ground heat fluxes had large variations among the schemes. The spatial patterns of the model-computed net radiation and surface temperature were generally similar among the schemes, and appear reasonable and consistent with observations of related variables, such as surface air temperature. The spatial mean patterns of latent and sensible heat fluxes were less similar than for net radiation, and the spatial patterns of the ground heat flux vary greatly among the 16 schemes. Generally, there is less similarity among the models in the temporal (interannual) variability of surface fluxes and temperature than there is in the mean fields, even for schemes with similar mean fields.