###### Abstract  
The occurrence of _Listeria monocytogenes_ in marine fish and fish market areas was investigated. Two hundred and eighty-eight samples (123 environmental samples--siphons, knives, cutting boards, floor, sinks, water, and ice--and 165 marine fish samples) were examined. Twenty-four isolates were characterized as _Listeria monocytogenes_ (five from environmental samples (4.0%) and 19 from fish samples (11.5%)). The strains were further characterized according to their antibiotic resistance, pathogenicity, and biofilm formation ability. They were molecularly serotypes as ILe (n = 22) and IVb (n = 2) possessed all the virulence genes tested (_intLA_, _inLB_, _inLC_, _inll_, _actLA_, _hlyA_, _inp_, _plcA_, and _prfA_), except for two strains lacking the _hlyA_ and _inp_ genes, respectively. All strains showed strong (41.7%) or moderate biofilm-producing ability (58.3%) and almost all showed resistance to at least one antibiotic, with the highest rates being observed against clindamycincin and vancomycin. The proteomic analysis by MALDI TOF revealed two distinct clusters that involved strains from fish only and those from both fish and the environment. The presence of _Listeria monocytogenes_ in the fish-market environment and marine fish, along with the pathogenicity and persistence characteristics of the seafood-related strains, emphasize the need for vigilance concerning the spread of this notorious foodborne pathogen. Listeria  
it is recognized as a major threat to public health due to the high rate of hospitalization (94% of cases) and mortality (30% of cases), mainly among people in vulnerable groups [8]. _Listeria monocytogenes_ persists in food processing facilities for long periods of time, even when appropriate hygiene measures are applied, mainly due to its biofilm formation ability on abiotic surfaces [9]. Furthermore, the contamination of food by this bacterium is quite severe since it is one of the few pathogens that can multiply at refrigeration temperatures [10]. The most suitable foods for the proliferation of _Listeria monocytogenes_ are non-thermally processed products, food kept in refrigeration for a long time, food produced under unsanitary conditions, and cooked and frozen ready-to-eat meals [11]. In the European Union, limits are set by Commission Regulation (EC) No. 2073/2005 in ready-to-eat food for the occurrence or enumeration of _L. monocytogenes_. The recent European Union One Health zoonoses report states that _L. monocytogenes_ was detected in 7.1% of ready-to-eat fish and fishery products, one of the highest among ready-to-eat foods in the European Union [7]. The prevalence of _Listeria monocytogenes_ in seafood depends on several factors, such as the geographic area, the water quality, the seasonality, and the discharge of agricultural effluents in water bodies ending up in the sea [12; 13; 14]. The prevalence of the pathogen usually varies between geographic regions; furthermore, the variation in prevalence and serotypes between different regions is mainly caused by environmental factors and climatic differences between countries. These differences may affect the presence and proliferation of _Listeria monocytogenes_ and, therefore, affect the risk posed by this foodborne pathogen. Additionally, the water quality and pollution levels prevailing in each region affect the prevalence of _Listeria monocytogenes_[12; 14]. In cases where the fish-rearing areas receive livestock effluents, the possibility of the occurrence of this pathogen in the seawater is augmented, resulting in the contamination of the aquatic animals and seafood produced there [13]. In addition, seasonal variations can play a vital role in the appearance and diversity of pathogenic bacteria in general and specifically of _Listeria monocytogenes_[15; 16]. A crucial factor in the interaction of _Listeria monocytogenes_ with seafood is the species and type of fish that came in contact with the pathogen.