Life-history traits and exploitation of the red shrimp, Aristeus antennatus (Risso, 1816) (Decapoda, Aristeidae) on the Algerian slope (south-western Mediterranean) have been studied through monitoring of the commercial trawl fishery between 1999 and 2006 at two different ports on the west coast, as well as through monthly biological sampling of these catches from April 2005 to September 2006. This information was completed with data from experimental bottom trawls, carried out in the area during 2003 and 2004. A continuous increase of the trawl fleet and the landings of red shrimp during the study period were detected. Although this fishery takes place only in a very limited part of the distribution range of the species (around depths of 300-525 m), experimental data gave a continuous increase of red shrimp density from 400 to 700 m. The Algerian fishery showed seasonal variation in yields, with a maximum during summer and autumn, although the average daily yields were clearly higher than those from other western Mediterranean fisheries. Experimental trawls detected two distinct demersal assemblages on the slope grounds of the study area, separated approximately by the 400 m isobath. Decapod crustaceans constituted the dominant group in these assemblages, with the pink shrimp (Parapenaeus longirostris (Lucas, 1846)) and the red shrimp as their most important and abundant species, and either shallower, or deeper than that isobath, respectively. Both species of shrimp showed one of the highest abundance indices estimated in the Mediterranean yet. Fishes were also important in these assemblages, the composition of which suggested high species diversity, with complex and extensive trophic webs. Monthly length frequency distribution of commercial catches showed that the carapace length (CL) of female shrimps ranged between 18 and 65 mm, while males ranged from 16 to 41 mm CL. Females represented more than 70% of the individuals caught, although the sex-ratio by length showed a predominance of males for individuals 18 mm CL and of females for individuals 25 mm CL, while their monthly development also showed a predominance of females from April to September and a similar proportion of sexes from October to March. Ripening gonads of females were mostly found from June to August, and the

The blackmouth catshark Galeus melastomus (Rafinesque, 1810) (Chondrichthyes Scyliorhinidae) is an accidentally caught species and it acts as a sentinel, by reflecting the state of the region's fish stocks. Its vulnerability to the impact of fishing, along with the low fertility and late reproduction, do not ensure a good renewal. Data, collected during 13 months from November 2015 to November 2016, were analysed to enrich our knowledge on the population, reproductive biology, growth, and feeding strategy of the blackmouth catshark from the Western coast of Algeria. A total of 551 specimens, 360 males and 191 females, were caught. Their size ranged from 25 cm to 56 cm for both sexes. The length of the first sexual maturity was stunted at 54 cm in females. The asymptotic length was deduced from the von Bertalanffy growth equation to be higher for males than females (females: L∞ = 51.79 cm; males L∞ = 52.14 cm) and the study of the height-weight relationship revealed allometric growth. 551 stomachs were examined and the vacuity index was found to be 63.75%. The preys identified belonged primarily to three major groups: Crustaceans, Osteichthyes, and Cephalopods. Our results show that the feeding strategy of G. melastomus is to be considered generalist and differs from one month to another.

Body morphometric characteristics and otolith shape described by elliptic Fourier descriptors analyses were carried out on European anchovy (Engraulis encrasicolus) samples collected from six locations in Algerian waters during the acoustic survey ALPEL2018 (south-western Mediterranean Sea, GFCM-GSA04). The discriminant analysis was applied over twelve morphometric body distances and 31 normalized elliptic Fourier descriptors. It highlighted significant difference between areas but with high overlapping. No significant difference was detected between males and females, or right and left otoliths. Hierarchical clustering analysis conducted on the mean form of body and otolith shape showed a clear geographical cline. The results indicate that the geographical trend is present with a high level of overlapping between the near areas, suggesting that European anchovies in Algerian waters are not completely isolated.

The objectif in the present study is description of a new species of Sphincteristomum Oshmarin, Mamaev & Parukhin 1961, named Sphincteristomum mediterraneae, which is described in Oran bay, Algeria. It parasitizes the intestine of naturally infected Pagellus erythrinus, Teleostei, Sparidae. The Pagellus erythrinus is in important food fish in the Mediterranean. This genus belongs to the family Apocreadiidae, sub family Schistorchiinae, characterized by an obvious oral muscular sphincter, into a large oral sucker, a disc-shaped acetabulum under the intestinal bifurcation, an ocular pigment scattered in the forebody, a sequence ovary and two testes in tandem and a I-shaped excretory bladder. In the new species, the digestive apparatus displays a hexagonal peculiar aperture, followed by a longitudinal slit, a waved pharynx, two long and broad caeca, with a thick internal wall of endothelial cells. Each caecum has a sub terminal anus. The female genital apparatus displays a transversally elongated ovary, under the acetabulum. On the side of the ovary, there is a small Mehlis gland. Under the ovary, there are two transverse converging vitelloducts. Lateral and extracaecal vitelline follicles, are spread near the caeca. They converge in the hindbody. The relatively short uterus is preovarian, mainly. It contains few large yellow eggs. Its distal part is creased transversally, just before ending in genital atrium. The male genital apparatus shows two lobed heart-shaped testes, post ovarian, in tandem. From the anterior edge of each testis, two spermiducts climb up and converge into a naked, curved or sinuous seminal vesicle, followed by a short prostate surrounded by few prostatic cells, and a narrow ejaculatory duct, opening in genital atrium. The genital pore is close to the acetabulum and the intestinal bifurcation. No cirrus pouch. The excretory system shows a relatively short tubular I-shaped bladder, reaching the inferior level of the second testis. Two thin excretory arms are seen until the forebody of the worms. The terminal excretory pore is closed by a small sphincter. In the same P. eryrthrinus, immature worms devoid of genitalia, young worms with genitalia devoid of eggs and ovigerous worms, live together with senile specimens. These last ones show still, oral sucker, diffuse vitelline follicles and very small and scattered ocular pigment.

Limpets constitute an important key species in the intertidal zone. The limpets’ assemblage is evaluated in Plane Island (Paloma Island, Algerian West coast) by detailed censuses which were performed in 8 zones in the main island and 9 islets. Results allowed the estimation of a total population of 3993 of the endangered Patella ferruginea (1.78ind/m), 1861 P. rustica (0.82ind/m), and 383 of the blue Mediterranean limpet P. caerulea (0.17 ind/m). The ferruginous limpet distribution around Plane Island was influenced by abiotic factors as hydrodynamics and the sea current direction. Conversely, anthropogenic factors had an important impact despite the island's distance from the mainland. This study finds that in the face of global warming, the island surface will be reduced, however limpets will have an important contribution to the island's areas and its conservation of biodiversity.