Demersal fishes were sampled using a large fish trawl during two surveys carried out in February and March 2004 and 2008 in the Ross Sea, and around seamounts and islands just to the north at 66°S. The distribution and abundance of 65 species collected in these surveys were examined to determine if demersal fish communities varied throughout the area, and what environmental factors might influence this. Species accumulation with sample frequency did not reach an asymptote, but the rate of new species was low suggesting data were adequate for describing the main components of the communities. Three broad assemblages were identified, in the southern Ross Sea (south of 74°S), central–northern Ross Sea (between latitudes 71°–74°S), and the seamounts further north (65°–68°S) where some species more typical of sub-Antarctic latitudes were observed. Multivariate analyses indicated that environmental factors of seafloor rugosity (roughness), temperature, depth, and current speed were the main variables determining patterns in demersal fish communities.

The community structure of shallow rocky reef fish fauna of the Azores Archipelago is described from underwater visual censuses carried out at eight areas (Terceira and Corvo Islands). A total of 52 fish species from 26 different families was observed, and the ten most abundant fish corresponded to 82.7% of all fish. Trophic categories are given for observed species with comments on distribution and densities along sampled depth strata. Mean densities along sampled strata were tested for significant differences. Sparidae, Labridae and Carangidae were the most speciose families being Diplodus sargus, Pagellus acarne, Coris julis, Thalassoma pavo and Tripterygion delaisi the most abundant species that consequently also accounted for the highest densities.

When reviewing the various fish-based community indicators aiming at assessing the ecological status of marine communities and/or ecosystems, a typology consisting of three major components emerges. The first component highlights the choice of relevant metrics associated with a level of organization (e.g. population or community). The second relies on the method used to combine the metrics (an aggregated indicator or a synoptic table). The third refers to the type of analysis (direct or indirect) that is used to establish the link between the metrics and a given pressure. In this paper we use the Vilaine coastal-estuarine fish communities as a case study to discuss and relate two different approaches to the suggested typology. The first approach (time-trend approach) is based on historical series of data, whereas the second approach (multi-metric index, MMI) is based on a geographic series including various French estuaries. They were developed or adapted from French studies but are representative of the approaches used in Europe. When applied to the case study, they differed in their diagnosis: the time-trend approach indicated that the bay of Vilaine habitat was deteriorating, whereas the MMI, which compares many French estuaries, indicated a good environmental state. Differences and complementarities between the approaches are thoroughly discussed with respect to the three mains components of the typology. This work appears at a particular moment, when several fish-based indicators are being developed in France and the rest of Europe. It intends to serve as an element of the ongoing reflection concerning the limitations of the various approaches that can be used to develop such indicators.

Marine sanctuaries are increasingly being promoted as tools for conservation and fisheries management. This study investigates the effects of protection over 19 years on substrate composition and fish communities in four marine sanctuaries and corresponding non-sanctuary areas in the Philippines and examines the importance of community support, management measures and enforcement of regulations on these ecological effects. Between 1981 and 2000, substrate cover variables were measured using line transects with scuba and snorkel surveys, and fish censuses (identification to family level) were conducted using scuba within a 500 m2 area. Semi-structured interviews collected data on community support for the sanctuaries, and observations and interviews established management and enforcement aspects of the sanctuaries. Over time, all sanctuaries showed improvements, or maintenance of, ecological variables compared with pre-enforcement times, with maintenance of hard coral cover and average increases of 8.3% in fish species richness and 54.9% in fish abundance. In comparison, non-sanctuary areas showed maintenance of the status quo or declines in ecological variables. However hard coral cover, fish abundances and fish species richness showed significant declines as well as increases in sanctuary areas. Community, management and enforcement factors were significantly related to positive ecological trends in sanctuary areas; management and enforcement were related to a wider variety of ecological factors than community score. Community support was significantly related to an increase in hard coral cover in deep areas. Enforcement of regulations was significantly related to an increase in abundance of fishery target fish species in sanctuary areas, and simple management measures were significantly related to an increase in abundance of large predators. Supportive communities that voluntarily implemented sanctuary regulations, improved enforcement, and small discrete cohesive communities may have facilitated the process of building this community support. Well-enforced sanctuaries that showed an increase in abundance of target species may have contributed to the maintenance of fish yields in adjacent non-sanctuary areas. The effects of sanctuary implementation varied on a case-by-case basis, influenced by environmental, biological, physical and human factors. However, a combination of community support, management measures and enforcement of regulations contributed towards positive ecological trends in sanctuary areas.

For last 20 years, the fish communities in the Central Delta of the Niger River have been subjected to: (i) two drought periods in 1973 and 1984, (ii) a dramatic increase of fishing and, (iii) the building of an electric-power dam in 1984. At different levels, these various factors modified the biological cycle of the fish which are adapted to the former hydrological cycles of the Niger and the Bani rivers. The Sahelian drought is responsible for a decrease in both flood duration and of the inundated area of floodplain which varies from 20 000 km2 to 5 000 km2. From 1968 to 1989, fish landings declined from 90 000 metric tons to 45 000 metric tons. During the same period, as fish catches fell, yields per hectare increased from 40 kg in 1968 to 120 kg in 1989. This phenomenon is linked to the decrease of the average age of the fish (69% of fish catches are under one year old) in response to the increased fishing mortality and natural mortality which is higher during the drought period. The increase in fish productivity is characterized by a depletion of species such as Gymnarchus niloticus, Polypterus senegalus, Gnathonemus niger, whose reproduction are linked to the floodplains and of species like Citharinus citharus and Clarotes laticeps which visit frequently flooded areas. Concurrently, families such as the Cichlidae or Clariidae, which are resistant to low oxygen concentration, increase. Species which are under one year old at first reproduction and have several spawning periods per year, are the more abundant in fish communities.

Les lagunes côtières doivent leur forte productivité aux échanges qu'elles entretiennent avec les eaux marines et continentales. Au Togo, en période de fermeture du cordon littoral (situation observée en 1994), la salinité est faible: 1 psu à Agbodrafo, ainsi que la diversité spécifique du peuplement étudié (Ish = 2,13). A l'inverse, après une période de communication avec la mer comme ce fut le cas en 1989, la salinité remonte sur l'ensemble du plan d'eau (7 psu à Agbodrafo) et les peuplements de poissons et de crustacés sont plus variés (Ish = 2.74) et à tendance marine ou marine-estuarienne (Liza, Caranx, Penaeus, Gerres...). Dans ce cas, les rendements élevés (300 à 400 kg/ha/an) s'expliquent par un enrichissement du milieu lagunaire dû aux apports marins et à l'introduction d'espèces marines. En situation d'isolement, les peuplements sont essentiellement estuariens et largement dominés par les Cichlidae et plus particulièrement Sarotherodon melanotheron qui représente à lui seul 50 % des captures totales. Dans un contexte de pêche particulièrement active, l'expansion de cette espèce est certainement due au fait qu'elle présente une reproduction continue. Néanmoins, les valeurs des rendements totaux observés (160 kg/h/dan), des tailles maximales (250 mm), des tailles moyennes de capture (120 mm) et des tailles de première maturité sexuelle (85 mm), inférieures aux valeurs rencontrées dans les autres lagunes de la région (Nigeria et Côte-d'Ivoire), semblent traduire une croissance de Sarotherodon plus faible au Togo. L'absence de communication avec la mer et la pression de pêche intensive seraient à l'origine d'une prolifération de cette espèce dont les fortes abondances entraîneraient à leur tour un ralentissement de la croissance.