• Energy Research

ABSTRACTClimatic variation can play a critical role in driving synchronous and asynchronous patterns in the expression of life history characteristics across vast spatiotemporal scales. The synchronisation of traits, such as an individual's growth rate, under environmental stress may indicate a loss of phenotypic diversity and thus increased population vulnerability to stochastic deleterious events. In contrast, synchronous growth under favourable ecological conditions and asynchrony during unfavourable conditions may help population resilience and buffer against the negative implications of future environmental variability. Despite the significant implications of growth synchrony and asynchrony to population productivity and persistence, little is known about its causes and consequences either within or among fish populations. This is especially true for long‐lived deep‐sea species that inhabit environments characterised by large‐scale interannual and decadal changes, which could propagate growth synchrony across vast distances. We developed otolith growth chronologies for three deep‐sea fishes (Etelis spp.) over 65° of longitude and 20° of latitude across the Indo‐Pacific region. Using reconstructed time series of interannual growth from six distinct Exclusive Economic Zones (EEZs), we assessed the level of spatial synchrony at the individual‐, population‐ and species‐scale. Across five decades of data, complex patterns of synchronous and asynchronous growth were apparent for adult populations within and among EEZs of the Pacific Ocean, mediated by shifts in oceanographic phenomena such as the Pacific Decadal Oscillation. Overall, our results indicate that the degree of synchrony in biological traits at depth depends on life history stage, spatiotemporal scales of environmental variability and the influence of ecological factors such as competition and dispersal. By determining the magnitude and timing of spatially synchronous growth at depth and its links to environmental variability, we can better understand fluctuations in deep‐sea productivity and its vulnerability to future environmental stressors, which are key considerations for sustainability.

Climate and weather have profound effects on economies, the food security and livelihoods of communities throughout the Pacific Island region. These effects are particularly important for small-scale fisheries and occur, for example, through changes in sea surface temperature, primary productivity, ocean currents, rainfall patterns, and through cyclones. This variability has impacts over both short and long time scales. We differentiate climate predictions (the actual state of climate at a particular point in time) from climate projections (the average state of climate over long time scales). The ability to predict environmental conditions over the time scale of months to decades will assist governments and coastal communities to reduce the impacts of climatic variability and take advantage of opportunities. We explore the potential to make reliable climate predictions over time scales of six months to 10 years for use by policy makers, managers and communities. We also describe how climate predictions can be used to make decisions on short time scales that should be of direct benefit to sustainable management of small-scale fisheries, and to disaster risk reduction, in Small-Island Developing States in the Pacific.

In several Pacific Island countries and territories (PICTs), rapid population growth and inadequate management of coastal fish habitats and stocks is causing a gap to emerge between the amount of fish recommended for good nutrition and sustainable harvests from coastal fisheries. The effects of ocean warming and acidification on coral reefs, and the effects of climate change on mangrove and seagrass habitats, are expected to widen this gap. To optimise the contributions of small-scale fisheries to food security in PICTs, adaptations are needed to minimise and fill the gap. Key measures to minimise the gap include community-based approaches to: manage catchment vegetation to reduce sedimentation; maintain the structural complexity of fish habitats; allow landward migration of mangroves as sea level rises; sustain recruitment and production of demersal fish by managing ‘source’ populations; and diversify fishing methods to increase catches of species favoured by climate change. The main adaptions to help fill the gap in fish supply include: transferring some fishing effort from coral reefs to tuna and other large pelagic fish by scaling-up the use of nearshore fish aggregating devices; developing fisheries for small pelagic species; and extending the shelf life of catches by improving post-harvest methods. Modelling the effects of climate change on the distribution of yellowfin tuna, skipjack tuna, wahoo and mahi mahi, indicates that these species are likely to remain abundant enough to implement these adaptations in most PICTs until 2050. We conclude by outlining the policies needed to support the recommended adaptations.