Maritime transportation is a major contributor to the world economy, but it may have a significant impact on marine mammals. The impact of shipping on cetaceans is especially noticeable in the Mediterranean Sea, which represents only 0.8% of the global ocean surface and yet it gathers 13% of the world sea trade. This leads to intense interactions with marine mammals, including fatal ones like ship strikes (i.e.: deadly collisions between a ship and a cetacean). 

While most cetacean species are at risk because of human activities, marine giants such as sperm and fin whales are mostly threatened by collisions and illegal driftnetting. 

The Pelagos Sanctuary and contiguous areas are known to be hot spots for ship collisions with fin whales. The events of collision risk undermining the recovery of this endangered population. 

As actions are required to reduce the risk of collisions, France, Italy, Monaco and Sapin in 2023 promoted the designation of a Particularly Sensitive Sea Areas (PSSA) in the north-western Mediterranean Sea by the International Maritime Organization (IMO). This area wholly includes the Pelagos Sanctuary and the Spanish Cetacean Migration Corridor, two Specially Protected Areas of Mediterranean Importance (SPAMI). Currently the north-western Mediterranean PSSA entails only mitigation measures of voluntary nature. However, in the near future mandatory mitigation measures, such as speed reduction or restricted areas, could be implemented to ensure the reduction of risk of collisions with fin and sperm whales particularly in certain seasons. Meanwhile various stakeholders, including the Pelagos Agreement, coast guards, shipping companies and scientists, are focusing on enhancing awareness on this issue and finding innovative mitigation tools. These include improving knowledge on collisions (e.g., models, behavior analysis) or testing technical solutions on collision avoidance strategies (e.g., tools to share whale observations, real-time acoustic detection).  The Pelagos Agreement is fully committed to these conservation efforts and assists and supports interested stakeholders and concerned governments.

Incidental entanglement in fishing nets is one of the major causes of cetacean mortality and other marine protected animals such as sea turtles, rays, etc. 

To quantify the impact of fishery-induced mortality on cetaceans, information on total bycatch and species’ abundance is required. This information is often lacking.

The repercussions of fishing on cetaceans have grown in parallel with the global development of this activity, not only because of incidental bycatch, but also because of increased pressure on the fish stocks on which cetaceans feed. 

Fishery is an important traditional and cultural activity and a source of livelihood for fishing businesses. Some fishermen have shown genuine goodwill, applying techniques that reduce bycatch, but much still needs to be done to ensure sustainable fishing.

All nautical activities involving either voluntarily or involuntarily approaching a marine mammal and their important habitats (e.g., breeding sites, feeding sites, etc.) are considered potential sources of disturbance and stress. Hence, they need to be correctly regulated.

Sea and land-generated pollution (biological, chemical, litter) 

The Mediterranean basin hosts a high density of inhabitants, fishing and commercial shipping activities, oil and gas extraction, and tourism. These activities, combined with an increase in the coastal industrial economy, have a great impact on the ecosystems. Cities’ sewage, industrial and incidental discharges, massive seasonal presence of bathers, are all important sources of persistent organic pollutants, emerging contaminants, marine litter and pathogens.

As apex predators with long life spans, cetaceans are very sensitive to environmental contaminants, particularly to legacy contaminants as heavy metals, legacy organic pollutants as polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), dichlorodiphenyltrichloroethane (DDTs), and emerging pollutants such as plastic additives and pharmaceuticals and personal care products (PPCPs). Persistent organic contaminants are chemical compounds of global concern due to their persistence in the environment, their ability to be transported over long distances and their effects on natural populations. They are biologically active chemicals that can bioaccumulate and biomagnify within marine food webs and have the potential to negatively affect marine organisms. Studies on cetaceans in the Mediterranean Sea and particularly in the Pelagos Sanctuary, have shown that these species have among the highest concentration of chemical pollutants in their tissues. 

Exposure to environmental compounds can cause immune system suppression and endocrine disruption which can affect population health. Increased infectious disease susceptibility, and neoplasia have also been linked to high levels of contaminants in marine mammals.

Marine litter is defined as any persistent, manufactured or processed solid material discarded, disposed, or abandoned in the marine environment. It is globally acknowledged as a major societal challenge of our times, due to its significant environmental, economic, social, political and cultural implications. 

The pollution of the oceans due to plastic waste generates great concern for both the scientific community and society. These materials accumulate in both shallow and deep waters, and especially in closed basins such as the Mediterranean Sea. Between 4.8 and 12.7 million tons of plastic waste were dumped into the ocean in 2010. Nowadays, marine litter is commonly observed across all oceans and marine ecosystems.

As highlighted by several ocean circulation models the Mediterranean Sea has been considered a sensitive plastic litter accumulation zone with an average concentration comparable to the great oceanic gyres. Marine megafauna, such as cetaceans and marine turtles, are particularly prone to ingestion and entanglement in marine litter. Entanglement can result in injury, drowning or strangulation of the organisms. Ingestion can cause pathology ranging from no discernible impact through to blockage of the digestive tract, suffocation and starvation. An increase in the number of cases of interaction of cetaceans with marine litter has been reported over the last five decades.

Global climate change is leading to a rapid reassessment of the planet’s flora and fauna, with uncertain prospects for the actual problems species will face shortly, including humans. 

Some effects are already well observable in the coastal environments of the Mediterranean, including in Marine Protected Areas, which are having to deal with drastic and sudden changes challenging the conservation of some habitats. Many native species are moving northwards, and alien species (i.e. not native to a certain ecoregion) have made their appearance due to the rising water temperature. Changes of the sea temperature can cause the redistribution of fish populations, which can consequently lead to a displacement of predators. Overheating of the water causes other essential problems such as, for example, an increased susceptibility to certain diseases. Reproductive cycles can also be affected. Sperm whales, for example, have a lower reproductive rate following periods of great heat at the water’s surface. Furthermore, the birth of offsprings for many species of marine mammals coincides with the period of maximum prey abundance. Climate change could cause a temporal mismatch between productivity and the period of greatest need of energy supply for mothers and calves during weaning periods.

An indirect effect of warming is the acidification of water, which leads to severe problems for many shell-building invertebrates. Cephalopods, on which many cetaceans feed, also suffer from the acidification of the water, experiencing difficulties in reproducing.  

> https://www.imo.org/en/MediaCentre/MeetingSummaries/Pages/SDC-9.aspx