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Abstract: Over recent decades, our understanding of climate change has accelerated greatly, but unfortunately, observable impacts have increased in tandem. Both mitigation and adaptation have not progressed at the level or scale warranted by our collective knowledge on climate change. More effective approaches to engage people on current and future anthropogenic climate change effects are urgently needed. Here, we show how species whose distributions are shifting in response to climate change, that is, ‘species‐on‐the‐move’, present an opportunity to engage people with climate change by linking to human values, and our deep connections with the places in which we live, in a locally relevant yet globally coherent narrative. Species‐on‐the‐move can impact ecosystem structure and function, food security, human health, livelihoods, culture and even the climate itself through feedback to the climate system, presenting a wide variety of potential pathways for people to understand that climate change affects them personally as individuals. Citizen science focussed on documenting changes in biodiversity is one approach to foster a deeper engagement on climate change. However, other possible avenues, which may offer potential to engage people currently unconnected with nature, include arts, games or collaborations with rural agriculture (e.g. new occurrences of pest species) or fisheries organisations (e.g. shifting stocks) or healthcare providers (e.g. changing distributions of disease vectors). Through the importance we place on the aspects of life impacted by the redistribution of species around us, species‐on‐the‐move offer emotional pathways to connect with people on the complex issue of climate change in profound ways that have the potential to engender interest and action on climate change. Read the free Plain Language Summary for this article on the Journal blog.

The Benguela Current is considered to be a major biogeographic barrier for tropical and warm-temperate marine fish, but there is limited knowledge regarding its influence on population sub-structuring of in more cold-tolerant species. Employing genetic variation within the mitochondrial DNA Control Region and six cross-specific nuclear microsatellite markers, a preliminary study was conducted to investigate population sub-structuring inArgyrosomus inodorus, a highly exploited, cold-temperate migratory species, across the Benguela Current region. Results revealed evidence of incipient genetic differentiation (mtDNAϕST= 0.092; nuclearFST= 0.036 andDST= 0.104,P< 0.05) between the two sampling sites, suggesting the presence of two regional populations. Estimates of contemporary migration rates between populations were low, and similar in range to those reported in tagging surveys. Although preliminary, these results suggest that the oceanographic features of the Benguela Current may have influenced the evolutionary history ofA. inodorus, and that the species is likely to be composed of two populations in the Benguela region. As the species is considered overexploited both in Namibia and South Africa, information on the distribution, population dynamics and long-term dispersal patterns across the Benguela Current region would support a comprehensive evaluation of genetic structure, which should be incorporated into fishery management arrangements. [ABSTRACT FROM PUBLISHER]

Contemporary patterns of genetic diversity and population connectivity within species can be influenced by both historical and contemporary barriers to gene flow. In the marine environment, present day oceanographic features such as currents, fronts and upwelling systems can influence dispersal of eggs/larvae and/juveniles/adults, shaping population substructuring. The Benguela Current system in the southeastern Atlantic is one of the oldest upwelling systems in the world, and provides a unique opportunity to investigate the relative influence of contemporary and historical mechanisms shaping the evolutionary history of warm-temperate fish species. Using the genetic variation in the mitochondrial DNA Control Region and eight nuclear microsatellite DNA loci, we identified the presence of two highly divergent populations in a vagile and warm-temperate fish species, Atractoscion aequidens, across the Benguela region. The geographical distributions of the two populations, on either side of the perennial upwelling cell, suggest a strong correlation between the oceanographic features of the system and the breakdown of gene flow within this species. Genetic divergence (mtDNA φST = 0.902, microsatellite FST = 0.055: probability of genetic homogeneity for either marker = p<0.001), absence of migrants (less than 1% per generation) between populations and coalescent estimates of time since most recent common ancestor suggest that the establishment of the main oceanographic features of the system (2 million years ago), particularly the strengthening and position of the perennial upwelling cell, is the most likely mechanism behind the observed isolation. Concordance between mitochondrial and nuclear genetic markers indicates that isolation and divergence of the northern and southern Benguela populations of A. aequidens occurred deep in the past and has continued to the present day. These findings suggest that the Benguela Current system may constitute an ancient and impermeable barrier to gene flow for warm-temperate fish species. [ABSTRACT FROM AUTHOR]

Catch‐and‐release (C&R) angling has grown in popularity due to increasing numbers of conservation‐minded anglers and regulations of recreational fisheries. C&R is often assumed to cause low mortality but can cause physiological and physical impairment. Fish metabolism and temperature interact to play a critical role in the biological functioning of fish. Understanding the relationship between temperature, fish metabolism, and physiological impairment is important for effective fisheries management and conservation, particularly for C&R angling in a changing thermal environment. We used respirometry to quantify post‐release metabolic stress and recovery of two popular Namibian angling species (Argyrosomus inodorus and A. coronus) subjected to simulated C&R angling across a range of temperatures. Metabolic stress and recovery time did not differ significantly between warm (A. coronus) and cold‐water (A. inodorus) species at any test temperature. However, several specimens of both species failed to recover physiologically and physically after 10 hours, thereby indicating C&R‐related impairment and potential for mortality. Given the predator‐rich environment of coastal waters in Namibia, best C&R practices are needed to minimise post‐release mortality. [ABSTRACT FROM AUTHOR]

In the marine environment, an increasing number of studies have documented introgression and hybridization using genetic markers. Hybridization appears to occur preferentially between sister-species, with the probability of introgression decreasing with an increase in evolutionary divergence. Exceptions to this pattern were reported for the Cape hakes (Merluccius capensis and M. paradoxus), two distantly related Merluciidae species that diverged 3-4.2 million years ago. Yet, it is expected that contemporary hybridization between such divergent species would result in reduced hybrid fitness. We analysed 1,137 hake individuals using nine microsatellite markers and control region mtDNA data to assess the validity of the described hybridization event. To distinguish between interbreeding, ancestral polymorphism and homplasy we sequenced the flanking region of the most divergent microsatellite marker. Simulation and empirical analyses showed that hybrid identification significantly varied with the number of markers, model and approach used. Phylogenetic analyses based on the sequences of the flanking region of Mmerhk-3b, combined with the absence of mito-nuclear discordance, suggest that previously reported hybridization between M. paradoxus and M. capensis cannot be substantiated. Our findings highlight the need to conduct a priori simulation studies to establish the suitability of a particular set of microsatellite loci for detecting multiple hybridization events. In our example, the identification of hybrids was severely influenced by the number of loci and their variability, as well as the different models employed. More importantly, we provide quantifiable evidence showing that homoplasy mimics the effects of heterospecific crossings which can lead to the incorrect identification of hybridization.