Reproductive resilience: a paradigm shift in understanding spawner‐recruit systems in exploited marine fish

A close relationship between adult abundance and stock productivity may not exist for many marine fish stocks, resulting in concern that the management goal of maximum sustainable yield is either inefficient or risky. Although reproductive success is tightly coupled with adult abundance and fecundity in many terrestrial animals, in exploited marine fish where and when fish spawn and consequent dispersal dynamics may have a greater impact. Here, we propose an eco‐evolutionary perspective, reproductive resilience, to understand connectivity and productivity in marine fish. Reproductive resilience is the capacity of a population to maintain the reproductive success needed to result in long‐term population stability despite disturbances. A stock's reproductive resilience is driven by the underlying traits in its spawner‐recruit system, selected for over evolutionary timescales, and the ecological context within which it is operating. Spawner‐recruit systems are species specific, have both density‐dependent and fitness feedback loops and are made up of fixed, behavioural and ecologically variable traits. They operate over multiple temporal, spatial and biological scales, with trait diversity affecting reproductive resilience at both the population and individual (i.e. portfolio) scales. Models of spawner‐recruit systems fall within three categories: (i) two‐dimensional models (i.e. spawner and recruit); (ii) process‐based biophysical dispersal models which integrate physical and environmental processes into understanding recruitment; and (iii) complex spatially explicit integrated life cycle models. We review these models and their underlying assumptions about reproductive success vs. our emerging mechanistic understanding. We conclude with practical guidelines for integrating reproductive resilience into assessments of population connectivity and stock productivity.     

Ecoviability for ecosystem‐based fisheries management

Reconciling food security, economic development and biodiversity conservation is a key challenge, especially in the face of the demographic transition characterizing many countries in the world. Fisheries and marine ecosystems constitute a difficult application of this bio‐economic challenge. Many experts and scientists advocate an ecosystem approach to manage marine socio‐ecosystems for their sustainability and resilience. However, the ways by which to operationalize ecosystem‐based fisheries management (EBFM) remain poorly specified. We propose a specific methodological framework—viability modelling—to do so. We show how viability modelling can be applied using four contrasted case‐studies: two small‐scale fisheries in South America and Pacific and two larger‐scale fisheries in Europe and Australia. The four fisheries are analysed using the same modelling framework, structured around a set of common methods, indicators and scenarios. The calibrated models are dynamic, multispecies and multifleet and account for various sources of uncertainty. A multicriteria evaluation is used to assess the scenarios’ outcomes over a long time horizon with different constraints based on ecological, social and economic reference points. Results show to what extent the bio‐economic and ecosystem risks associated with the adoption of status quo strategies are relatively high and challenge the implementation of EBFM. In contrast, strategies called ecoviability or co‐viability strategies, that aim at satisfying the viability constraints, reduce significantly these ecological and economic risks and promote EBFM. The gains associated with those ecoviability strategies, however, decrease with the intensity of regulations imposed on these fisheries.     

Effect of environmental conditions on the seasonal and inter‐annual variability of small pelagic fish abundance off North‐West Africa: The case of both Senegalese sardinella

The objective of this study was to assess the effect of environmental variations on the abundance of Sardinella aurita and Sardinella maderensis in Senegalese waters in the upwelling system. Monthly data indicating the abundance of sardinella were first estimated from commercial statistics, using Generalized Linear Model from 1966 to 2011. Abundance indices (AIs) were then compared with environmental indices, at the local scale, a Coastal Upwelling Index (CUI) and a coastal Sea Surface Temperature (SST) index, and on a large scale, the North Atlantic Oscillation (NAO), the Atlantic Multidecadal Oscillation (AMO) and the Multivariate El Niño Southern Oscillation Index (MEI), using correlations and times series analyses. The results showed that the abundance of sardinella is determined by a strong seasonal pattern and inter‐annual fluctuations. The abundance of S. aurita peaked in spring and in autumn, whereas that of S. maderensis peaked in the warm season (July–September). The trend of the sardinella abundance was significantly correlated with the CUI, especially in autumn and spring. Interannual fluctuations of S. maderensis and S. aurita abundance are, respectively, driven by the precocity and the duration of the upwelling season that is attributed to distinct migration patterns. Both sardinella species also respond with a delay of around 4 years to the winter NAO index and the autumn CUI, and the AMO index, respectively, both related to migration patterns. The wide variations in sardinella biomass are caused by variations in environmental conditions, which should be considered in the implementation of an ecosystem‐based approach in sardinella stocks management.     

Summer mortality of hatchery-produced Pacific oyster spat (Crassostrea gigas). I. Estimation of genetic parameters for survival and growth

The multidisciplinary project “MOREST” aims to improve our understanding of causes of summer mortality in Crassostrea gigas juveniles in France and to reduce its impact on oyster production. As part of the MOREST project, 43 full-sib families nested within 17 half-sib families were produced, planted out and tested in 3 sites during summer 2001 to assess to what extent genetic variability exists for this trait. A strong genetic basis was found for survival as narrow-sense heritability estimates ranged from 0.47 to 1.08, with higher values in sites where summer mortality was higher. Genetic correlations across sites were positive and very high for survival, indicating no genotype by environment interaction. In contrast, lower genetic variation was observed for growth in all sites. Finally, genetic correlations between growth and survival were low, in all sites. Selective breeding in a single site should therefore be an efficient means of improving survival in oysters less than one year old along the French Atlantic and Channel coastlines with only very limited effects on growth. As yield mostly depends on survival and growth, this approach should significantly improve harvestable yield. Possible reasons why a high genetic variance for survival appears to be maintained in wild populations are discussed.     

Changes in fatty acid and sterol composition during oogenesis in the pearl oyster Pinctada margaritifera

The fatty acid and sterol composition of the oyster Pinctada margaritifera during oogenesis and in eggs was analysed. No major differences were observed during oogenesis, but the egg composition was significantly different from that of gonads. The amount of saturated fatty acids was the highest in eggs and the C16:0 predominant (P<5%); by contrast, the amount of 22:6(n‐3) was significantly lower (P<5%) than in gonads. No major differences were observed for the polar lipid (PL) composition during oogenesis. The main free sterols in gonads and eggs were cholesterol and brassicasterol. Among free sterols, the proportion of cholesterol diminished continuously from the beginning to the end of gonad maturation, and this decrease persisted in eggs after spawning. Cholesterol represented 40% to 55% of the sterol ester encountered in gonad and eggs. This study allowed us to investigate the fatty acid and sterol composition during oogenesis of the pearl oyster P. margaritifera, leading to a clearer understanding of the nutritional requirements of pearl oyster during the reproduction process.     

A three‐year field study on the short‐term effects of insecticides used to control cereal aphids on plant‐dwelling aphid predators in winter wheat

Short‐term effects of six insecticides used to control aphids were assessed in wheat on plant‐dwelling aphid predators. Products were applied to small plots of winter wheat in June or at the beginning of July and the densities of predators were estimated three days after treatment using a beating method. Insecticides were tested in 1994, 1995 and 1997 at a single dose, corresponding to their maximum recommended field rate in Belgium. Fluvalinate and esfenvalerate did not significantly reduce catches of syrphid larvae compared to the control but ladybirds were affected by these compounds. Pirimicarb was the only product tested that had no effect on ladybirds. However, syrphid larvae appeared sensitive to this product. Cyfluthrin, deltamethrin and phosalone reduced catches of both syrphids and ladybirds. Populations of lacewing larvae were unaffected by any of the insecticide treatments. Syrphid larvae were the most abundant aphid predator and Episyrphus balteatus the most common species. Ladybirds (Coccinella septempunctata and Propylea quatuordecimpunctata) were less numerous and only a few Chrysoperla carnea larvae were recorded. These results indicate that products that are less toxic to syrphid larvae, like esfenvalerate and fluvalinate, may be preferable to other compounds to control cereal aphids in wheat in spring and early summer. However, other criteria, such as the effectiveness of the different aphid‐specific predators, cost, efficacy of the treatment and side effects on other aphid antagonists (including parasitic hymenoptera and polyphagous predators) must also be taken into consideration. © 2000 Society of Chemical Industry     

Review: Resistance as a concomitant of modern crop protection

This paper reviews the impact of resistance to fungicides and insecticides/acaricides on the way crop protection is practised. It is now clear that resistance can develop to virtually any crop-protection product, in any pest, fungal pathogen or even weed. As a limiting factor in crop protection, it is a fact of life. A positive side-effect is the precision with which products are used today, with increasing implementation of Integrated Pest Management (IPM) programmes. This is a vital step towards sustainability. This paper describes: past experiences; current status of resistance; how resistance management influences current crop protection practices; regulatory aspects; and the outlook for the future. It concludes that EU regulations on resistance management must be simple and workable. Chemicals will continue to have a central role in optimising yields from the world's crops, as new tools, including biotechnology, become available for crop protection and resistance management. The crop-protection industry's innovations and product stewardship programmes will contribute to sustainable agriculture. This will provide continued benefits to users, the environment and society. ©1997 SCI     

Response of Scotian Shelf silver hake (Merluccius bilinearis) to environmental variability

Commercially‐exploited fish populations are not only shaped by fishing pressure, but also by the dynamics of their environment. By quantifying the influence of environmental variability, fisheries management advice can be improved and uncertainties reduced. To this end, we developed statistical models of the response of Scotian Shelf silver hake stock metrics to variability in zooplankton community composition and phenology over the past 18 years and in the physical environment since 1985. Dominant modes of variability in these pelagic habitat indicators were characterized using principal component analysis, and the relationships of silver hake condition, abundance, and recruitment to pelagic habitat variability were assessed using generalized additive models. Condition was largely modulated by the onset and duration of the spring bloom, which controls food availability. In contrast, adult abundance was governed by composition of the zooplankton community and bottom‐water temperature, which dictates the distribution of silver hake. Finally, recruitment was affected by both thermal conditions and food availability. Our results presented here form the basis for qualitative assessment of ecosystem attributes and the influence on silver hake stock productivity.     

Effect of short heat shocks applied during grain development on wheat (Triticum aestivum L.) grain proteome

In the field, developing cereal grains are often exposed to short periods of very high temperature (>35 °C) that may dramatically affect grain yield and flour quality. Here we report on the effect of 4 h of heat shock (HS) at 38 °C applied on four consecutive days during the linear phase of storage compound accumulation on grain proteome of the winter bread wheat. At maturity the average single grain dry mass and the total quantity of nitrogen per grain were 25% and 16%, respectively lower for the HS treatment than for the control, resulting in a higher (+1.6% dm) grain protein concentration in HS grains. Individual albumin–globulin, gliadin and glutenin protein fractions from grains collected just before the HS and 1, 8, and 26 (ripeness maturity) days after the HS were quantified then analysed by 2-dimensional electrophoresis followed by MALDI-TOF and MS/MS identification. The quantity per grain of 10 gliadins and 3 low molecular weight glutenin subunit proteins were significantly affected by HS. Thirty-eight HS responsive albumin and globulin proteins were identified, including several enzymes involved in carbohydrate, redox, and lipid metabolisms. One protein was transitorily induced in response to HS. Detailed discussion of the expression of these proteins is presented.     

Evaluating a novel analgesic strategy for ring castration of ram lambs

Objective To evaluate the analgesic efficacy of the NSAIDs flunixin and meloxicam administered locally to the scrotum before ring castration. Study design Randomised, controlled, prospective study. Animals Forty eight single born male Merino lambs. Methods Lambs, aged approximately 4 weeks, were allocated to four groups for castration. Groups were: sham control; castration + saline; castration + flunixin; castration + meloxicam. Drugs (5 mL) were administered subcutaneously around the circumference of the scrotum immediately before castration. Cortisol, rectal temperature, haematology and plasma haptoglobin were measured before and up to 48 hours after treatment. Behaviour recorded by video for 12 hours after treatment was classified as pain avoidance behaviours in the first hour and postural behaviours in three 4 hour intervals. Results Ring castration (saline group) induced a bi‐phasic increase in cortisol with peaks at 90 minutes and 24 hours but no significant changes in haematology, haptoglobin or rectal temperature. Pain avoidance behaviours were increased and teat seeking decreased. Normal lying and normal standing postures were decreased and abnormal ventral lying, statue standing, abnormal standing and total abnormal postures increased. Flunixin decreased cortisol at 90 minutes (60.3 versus 117.3 nmol L^?1) and cortisol AUC (0–6 hours), decreased elevated leg movement (2.5 versus 5.4 events) and sum of pain avoidance behaviours (8.5 versus 16.7 events), improved time spent in normal ventral lying and decreased abnormal ventral lying and total abnormal postures compared to saline treated lambs. In a similar contrast, meloxicam caused non‐significant decreases in cortisol at 90 minutes, cortisol AUC (0–6 hours) and pain avoidance behaviours, and significantly improved the postural behaviours normal ventral lying (26.7 versus 15.4%) and normal standing (13.9 versus 7.5%), and reduced abnormal standing and total abnormal postures. Physiological and behavioural responses associated with ring castration for both NSAID treatment groups were generally greater than sham controls. Conclusions and clinical relevance Locally administered NSAIDs provided partial analgesia for ring castration.