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Photobacterium damselae subspecies damselae, an abundant, generalist marine pathogen, has been reported in various cetaceans worldwide. We report a bottlenose dolphin in the eastern Mediterranean Sea that was found stranded and dead. The dolphin had a severe case of chronic suppurative pneumonia and splenic lymphoid depletion caused by this pathogen.

We investigated the presence and diversity of cetaceans in the Mediterranean Sea, analysing the data collected by 32 different research units, over a period of 15 years (2004–2018), and shared on the common web-GIS platform named Intercet. We used the encounter rate, the species prevalence, and the Shannon diversity index as parameters for data analysis. The results show that cetacean diversity, in the context of the Mediterranean basin, is generally quite low when compared with the eastern Atlantic, as few species, namely the striped dolphin, the bottlenose dolphin, the fin whale, and the sperm whale, dominate over all the others. However, some areas, such as the Alboran Sea or the north-western Mediterranean Sea, which includes the Pelagos Sanctuary (the Specially Protected Area of Mediterranean Interest located in the northern portion of the western basin), show higher levels of diversity and should be considered hotspots to be preserved. Primary production and seabed profile seem to be the two main drivers influencing the presence and distribution of cetaceans, with the highest levels of diversity observed in areas characterized by high levels of primary production and high bathymetric variability and gradient. This collective work underlines the importance of data sharing to deepen our knowledge on marine fauna at the scale of the whole Mediterranean Sea and encourages greater efforts in the networking process, also to accomplish the requirements of the Marine Strategy Framework Directive, with particular reference to Descriptor 1: biological diversity is maintained.

Viruses are among the most abundant and diverse biological components in the marine environment. In finfish, viruses are key drivers of host diversity and population dynamics, and therefore, their effect on the marine environment is far-reaching. Viral encephalopathy and retinopathy (VER) is a disease caused by the marine nervous necrosis virus (NNV), which is recognized as one of the main infectious threats for marine aquaculture worldwide. For over 140 years, the Suez Canal has acted as a conduit for the invasion of Red Sea marine species into the Mediterranean Sea. In 2016–2017, we evaluated the prevalence of NNV in two indigenous Mediterranean species, the round sardinella (Sardinella aurita) and the white steenbras (Lithognathus mormyrus) versus two Lessepsian species, the Randall’s threadfin bream (Nemipterus randalli) and the Lessepsian lizardfish (Saurida lessepsianus). A molecular method was used to detect NNV in all four fish species tested. In N. randalli, a relatively newly established invasive species in the Mediterranean Sea, the prevalence was significantly higher than in both indigenous species. In S. lessepsianus, prevalence varied considerably between years. While the factors that influence the effective establishment of invasive species are poorly understood, we suggest that the susceptibility of a given invasive fish species to locally acquired viral pathogens such as NVV may be important, in terms of both its successful establishment in its newly adopted environment and its role as a reservoir ‘host’ in the new area.

In contrast to numerous documented pathogens and infectious diseases of aquaculture, there is a lack of baseline data and information regarding pathogenic agents’ prevalence in wild marine fish populations. This study focused on two common fish pathogenic microorganisms, namely Mycobacterium species and Vibrio species, both of which are known to be major causes of fish loss, occasionally to the extent of being a limiting factor in fish production. Both microorganisms are known as zoonotic agents. In total, 210 wild marine indigenous and Lessepsian fish from four different species from the eastern Mediterranean Sea were sampled and tested for Vibrio species and Mycobacterium species during a two-year period (2016–2017). Using PCR with 16S rRNA primers, we detected different strain variations of Mycobacterium species and Vibrio species and, based on the sequencing results, the overall prevalence for Vibrio species in wild fish in 2016 was significantly higher compared to 2017. No significant difference was detected for Mycobacterium species prevalence in wild fish between 2016 and 2017. In addition, 72 gilthead seabream (Sparus aurata) from an Israeli offshore marine farm were also examined during the two-year period (2017–2018). The results suggest that Mycobacterium species prevalence was significantly higher in 2018, while in 2017 there was no positive results for Mycobacterium species. In addition, there was no significant difference between both years in regard to the prevalence of Vibrio species for maricultured fish. These results highlight the necessity of continuous molecular monitoring in order to evaluate the prevalence of pathogenic microorganisms in both wild and cultured fish populations.

Streptococcus agalactiae is one of the most important fish pathogenic bacteria as it is responsible for epizootic mortalities in both wild and farmed species. S. agalactiae is also known as a zoonotic agent. In July 2018, a stranded wild sandbar shark (Carcharhinus plumbeus), one of the most common shark species in the Mediterranean Sea, was found moribund on the seashore next to Netanya, Israel, and died a few hours later. A post-mortem examination, histopathology, classical bacteriology and advanced molecular techniques revealed a bacterial infection caused by S. agalactiae, type Ia-ST7. Available sequences publicly accessible databases and phylogenetic analysis suggest that the S. agalactiae isolated in this case is closely related to fish and human isolates. To the best of our knowledge, this is the first description of a fatal streptococcosis in sandbar sharks.

We would like to change the authors’ affiliation of paper [...]

On 8 May 2010, a gray whale was sighted off the Israeli Mediterranean shore and twenty-two days later, the same individual was sighted in Spanish Mediterranean waters. Since gray whales were last recorded in the North Atlantic in the 1700s, these sightings prompted much speculation about this whale's population origin. Here, we consider three hypotheses for the origin of this individual: (1) it represents a vagrant individual from the larger extant population of gray whales found in the eastern North Pacific; (2) it represents a vagrant individual from the smaller extant population found in the western North Pacific; or (3) it represents an individual from the previously thought extinct North Atlantic population. We believe that the first is the most likely, based on current population sizes, on known summer distributions, on the extent of cetacean monitoring in the North Atlantic and on the results of a performed route analysis. While it is difficult to draw conclusions from such singular events, the occurrence of this individual in the Mediterranean coincides with a shrinking of Arctic Sea ice due to climate change and suggests that climate change may allow gray whales to re-colonize the North Atlantic as ice and temperature barriers to mixing between northern North Atlantic and North Pacific biomes are reduced. Such mixing, if it were to become widespread, would have implications for many aspects of the marine conservation and ecology of these two regions.

In September 2020, a male common dolphin (Delphinus delphis) was found dead on a beach near Bat-Yam, Israel. A small, raised, well circumscribed penile lesion (i.e., mass) was identified and removed for histology and molecular characterizations. By histology, the penile mass presented focal keratinization of the squamous epithelium and a mild ballooning of acanthocytes in lower epithelium levels, as well as features compatible with viral plaques, and tested positive for a gammaherpesvirus through molecular characterization analyses. Tissue samples from the lungs, liver, and spleen, however, tested negative for herpesvirus infection. The gammaherpesvirus detected herein is similar to other isolates found in several areas worldwide in different cetacean species. This is the first reported case of gammaherpesvirus infection in dolphins from the eastern Mediterranean Sea, indicative of the need for long-term assessments to create viral infections databases in cetaceans, especially in a climate change context, which is likely to intensify infectious disease outbreaks in marine mammals in the future.

Streptococcosis is an infectious bacterial disease of both homeotherms and poikilotherms. Among the Streptococcus species that infect marine animals, Streptococcus agalactiae has the broadest host spectrum, including different aquatic organisms in freshwater and marine environments. The common dolphin ( Delphinus delphis ) is categorized as Endangered in the Mediterranean Sea. There are few reports of a streptococcal infection of D . delphis , caused by Streptococcus phocae and Streptococcus iniae . Here we report the isolation and identification of S . agalactiae in a stranded, wild male common dolphin that was found dead in September 2020 on the seashore next to the city of Bat-Yam, Israel. The carcass was fresh with a moderate nutritional status and with no apparent fishing gear or other anthropogenic-related signs. A post-mortem examination did not reveal an apparent cause of death, but further laboratory analysis demonstrated a S . agalactiae bacterial presence in urine, lungs and pericardial fluid that was characterized as type Ia-ST7 by whole genome sequencing. Interestingly, this isolate was found to be almost identical to another isolate recently recovered from a wild sandbar shark ( Carcharhinus plumbeus ) in the same area in Israel, the eastern Mediterranean Sea.

The last authenticated reports of monk seals along the Israeli coastline were in 1953 of a single animal in an underwater cave near the Lebanese border; and in 1958 of another single animal in the Dor/Tantura lagoon, located in the cen-tral part of the coast (Dolev & Perevolotsky, 2004). [...] recently, there have been no further reported observations of the species in the country.