A broad range of marine species have been named as marine megafauna, however providing a precise definition of this term is difficult. It is not a taxonomically defined group, as it includes sea mammals, birds, reptiles, large fish and elasmobranchs (Fig. 1). Overall, marine megafauna species are large vertebrates that depend on marine resources for their food. These mobile species are generally at the top of their trophic food webs and have none or few predators. From the tiny storm-petrel to the gigantic blue whale, this group is biologically diverse and brings together species which cannot be strictly defined by morphological or physiological similarities. Rather, our perception of marine megafauna as a coherent group is based on ecological similarities and shared conservation issues. These species are exposed to similar threats and generally show limited resilience due to their intrinsic life history traits such as low fecundity rates and high longevity. Consequently, they share common conservation challenges (e.g. Hooker and Gerber, 2004; Lascelles et al., 2014). The conservation of marine megafauna intrinsically deserves particular attention. First, these species can be exposed to intense and cumulative pressures. Over-exploitation, incidental catches, high contaminant burdens, entanglement in or ingestion of macroand micro-litter, underwater noise, collisions, global environmental changes and reductions in the availability of food resources are widespread pressures shared by several or all the taxa constitutive of marine megafauna. Consequently, many marine megafauna populations currently have a critical conservation status (Lascelles et al., 2014). Moreover, the low fecundity and long generation time often limit the capacity of collapsed populations to quickly recover. The recovery process typically takes decades in cetaceans, petrels or sharks; and their current conservation status often results from pressures of the last century cumulated with current pressures (e.g. Baker and Clapham, 2004: Lotze et al., 2011). Beyond species themselves, marine megafauna are a key element of many marine conservation strategies. Including some of the most charismatic marine species, large marine vertebrates are generally used as flagships to mobilize society at large on conservation issues. Moreover, they can function as umbrella species due to their large home ranges and high trophic level. Indeed, conservation measures focusing upon marine megafauna often benefit lower trophic level species, positively impacting marine habitat protection (Hooker and Gerber, 2004). They also have the potential to act as sentinel species and inform the ecological status of other less visible compartments of marine ecosystems (Simberloff, 1998; Zacharias and Roff, 2001).

Conservation science for marine megafauna in Europe: Historical perspectives and future directions

• The main observed effects of climate change on marine mammals globally have been geographical range shifts and loss of habitat through ice cover loss, changes to the food web, increased exposure to algal toxins and susceptibility to disease. • Climate-change impacts on marine mammals are particularly evident in polar regions where there has been physical loss of sea-ice habitat. Species most affected include polar bear, walrus, bearded seal, ringed seal, and narwhal. • Earlier and more-extensive phytoplankton blooms in subpolar and polar regions due to increased solar radiation leading to enhanced thermal stratification and hence higher productivity may have helped population increases in some baleen whale species, such as bowhead whale. • In mid-latitudes in the Northern Hemisphere such as around the British Isles, geographical range shifts appear to be occurring, with northward extensions of the range of warmer water species, such as striped dolphin, short-beaked common dolphin, and Cuvier’s beaked whale, and possible range contractions of cold-water species such as white-beaked dolphin. • In low latitudes where sea temperatures are highest, some species (e.g. bottlenose dolphin, baleen whales, manatees) have experienced occasional mass die-offs linked to the presence of algal toxins. These may now also be affecting marine mammal species in mid-latitudes, such as Californian sea lions and harbour seals. • Continued rises in sea temperature could result in a shift in the species composition for cetaceans around the British Isles, with increased biodiversity particularly of subtropical and warm temperate pelagic species. • Marine mammal species that traditionally make long-distance seasonal migrations (e.g. most baleen whales) will likely arrive earlier or remain in high latitudes for longer, with increased breeding attempts. Citation: Evans, P.G.H and Waggitt, J.J. (2020) Impacts of climate change on marine mammals, relevant to the coastal and marine environment around the UK. MCCIP Science Review 2020, 421–455.

/pdf/impacts-of-climate-change-on-marine-mammals-relevant-to-the-4vqr7yhxe3.pdf

Impacts of climate change on marine mammals, relevant to the coastal and marine environment around the UK

La Liste rouge des espèces menacées en France - Chapitres de la Faune vertébrée de Guyane

: Competitive interactions between marine mammals and fisheries represent some of the most complex challenges in marine resource management worldwide. The development of commercial fisheries and recovering marine mammal populations have contributed to a decrease in fish availability. ecosystem-based fisheries management (EBFM) can counteract this decrease, achieving the EBFM objectives faces certain major obstacles including insufficient or unreliable data, inapplicable assessment models, as well as inadequate management decisions that do not account for fisheries-induced morphological alterations (FIMA) and marine mammal management. Despite a body of evidence addressing various aspects of marine mammal−fisheries competition, little is known about the effects of marine mammal−fisheries biological interactions affecting the fish viability and food web stability. We review the research on marine mammal− fisheries competitive biological interactions (hereafter biological competition) by focussing on (1) the prerequisites for marine mammal−fisheries biological competition and the relevant metho dologies to explore them and (2) recent studies revealing the implications of FIMA and trophic interactions for the biological competition. We also discuss the implications of FIMA, eco-evolu-tionary feedback and prey−predator dynamics for EBFM implementation in contemporary harvested ecosystems. Our main findings reveal a lack of data about marine mammals’ prey choice and selectivity, the need for better representation of marine mammals in modelling approaches and lastly, the necessity for additional research linking FIMA, trophic interactions and the EBFM objectives. To conclude, interdisciplinary approaches may serve to link all of the efforts needed to effectively and holistically support the implementation of EBFM. papers selection marine first literature random key-words: ‘fisheries’, specific used random of keywords: ‘cetaceans’, ‘pinnipeds’, ‘sea otter’, ‘fisheries’, ‘competition’, ‘observations’, ‘diet’, ‘feed-ing ecology’, ‘modelling’, ‘consumption’ and ‘ecosys-tem The third literature to the second specific area random of the keywords: ‘marine mammals’, -ped’, ‘cetaceans’, ‘sea otter’, ‘ecosystem-based’, ‘com-munity’, ‘fisheries-induced’ ‘inter-disciplinary’.

/pdf/competition-between-marine-mammals-and-fisheries-in-4mi9fej9ju.pdf

Competition between marine mammals and fisheries in contemporary harvested marine ecosystems

There are numerous examples of phenological shifts that are recognized both as indicators of climate change and drivers of ecosystem change. A pressing challenge is to understand the causal mechanisms by which climate affects phenology. We combined annual population census data and individual longitudinal data (1992-2018) on grey seals, Halicheorus grypus, to quantify the relationship between pupping season phenology and sea surface temperature. A temperature increase of 2°C was associated with a pupping season advance of approximately seven days at the population level. However, we found that maternal age, rather than sea temperature, accounted for changes in pupping date by individuals. Warmer years were associated with an older average age of mothers, allowing us to explain phenological observations in terms of a changing population age structure. Finally, we developed a matrix population model to test whether our observations were consistent with changes to the stable age distribution. This could not fully account for observed phenological shift, strongly suggesting transient modification of population age structure, for example owing to immigration. We demonstrate a novel mechanism for phenological shifts under climate change in long-lived, age- or stage-structured species with broad implications for dynamics and resilience, as well as population management.

https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.2021.2284

Climate causes shifts in grey seal phenology by modifying age structure.

Grey (Halichoerus grypus) and harbour seals (Phoca vitulina) are sympatric seal species, but they display distinct strategies of habitat use and connectivity between haulout sites. The distribution patterns and variations in relative abundance of both species were investigated along the French coast of the English Channel, at the southern limit of their range where seal numbers are increasing. Regular censuses conducted at all main haulout sites in mainland France showed significant seasonal variations at most sites, with more harbour seals counted during summer (breeding and moulting seasons), and more grey seals during summer only in the eastern English Channel. Trends in maximum haulout numbers at haulout sites showed a significant increase over the last five years, ranging from 9.7 to 30.9% per year for harbour seals, and from 5.8% (in the western English Channel) to 49.2% (in the eastern English Channel) per year for grey seals. These rates of increase in grey seal numbers are not linked to local pup production and most probably result from seal movements from the southwest British Isles and the North Sea, respectively. Aerial surveys conducted across the English Channel showed that most seal observations at sea were concentrated in the north-eastern English Channel. Telemetry showed that the 28 harbour seals tracked remained highly coastal, within a radius of 100 km from their haulout sites, and did not move to other known colonies. Grey seals moved much greater distances, reaching up to 1200 km from their capture site. More than half of the 45 grey seals tracked crossed the English Channel, especially during the breeding season, moving to known colonies in the southwest British Isles and the North Sea. Combining individual tracks and long-term surveys of the seal populations allowed a better understanding of the dynamics of these populations and their connectivity at a larger regional scale. The findings provide direct information for the management of grey and harbour seals within the frame of the Marine Strategy Framework Directive, and highlight focus areas where potential interactions between the two species should be monitored.

/pdf/grey-and-harbour-seals-in-france-distribution-at-sea-1r1mml0hca.pdf

Grey and harbour seals in France : distribution at sea, connectivity and trends in abundance at haulout sites

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Grey and harbour seals in France : distribution at sea, connectivity and trends in abundance at haulout sites