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4.1 Overall Impacts

The ocean is used for a wide range of human consumptive and non-consumptive uses providing recreation, food, livelihood, energy and pharmaceuticals. It is also used for activities such as transportation, defence, mining, conservation and scientific research (Richardson, 2003; Rosenberg, 2003). Ample documentation of these uses can be found on the web-based UN Atlas of the Oceans ( Non-fishing activities, whether coastal or continental, may have major impacts on the aquatic ecosystems through contamination, habitat modifications and alteration of freshwater flows (FAO, 1995a). The relevance to EAF stems from the fact that most of these impacts will threaten fisheries sustainability, either reducing resource productivity, stability and resilience to fishing, or reducing the quality of the fish as food through contamination.

Through land drainage, sewage, river outflow, wind and rainfall, such economic activities as agriculture, manufacturing or chemical industries, incineration of toxic wastes, human settlements, etc., release excess nutrients (e.g. nitrates, phosphorus) as well as contaminants (e.g. polychlorinated biphenyls (PCBs), mercury, dioxin), radioactive wastes, oil, antifouling paints (tributyl tin), human pathogens (e.g. cholera, salmonella), plastic and other debris. Coastal activities, including human settlements and tourism, often result in conversion and destruction of habitats of high relevance to fisheries such as estuaries or coastal wetlands used by fishery resources as reproduction, nursery or feeding areas, reducing fisheries productivity and resilience. Irrigation and production of hydroenergy reduce freshwater inflows into the oceans, resulting in modification or suppression of seasonal floods (as in the Nile), reducing or eliminating key environmental signals and reducing influx of nutrients. Dams and drying-up of streams, together with mining of gravel and sand and deforestation, modify the quality of habitats and alter or interrupt the reproductive migration processes of many species of marine fish (e.g. salmon, sturgeon). Together, these impacts result in eutrophication, harmful algal blooms (red tides) (for more details on harmful algal blooms, see, accidental death of animals through entanglement in (or ingestion of) debris; food contamination, human diseases, climate and sea-level changes; UV and temperature changes with impacts on primary productivity and biological habitats (such as coral bleaching) and can lead to total eradication of productive habitats (e.g. in the dried up Aral Sea).

4.2 Relative Importance of Fisheries and Other Impacts

Assessing the scale of fisheries effects relative to other impacts can be difficult, because of confounding and interacting combinations with other anthropogenic effects (e.g. pollution, habitat degradation, climate change) and natural variability of environmental factors. In the early 1970s, pollution and habitat degradation originating from land-based activities were considered to be the main factors of fisheries degradation (Stevenson, 1973). More recent publications hold that excessive fishing has become the main destabilizing factor of ecosystems, directly, through removals and associated impacts, as well as indirectly, through the aggravation of eutrophication and subsequent oxygen depletion (Jackson et al., 2001).

While fishing activities are generally fairly well described and their impact on resources have been studied and documented for decades, land-based sources pollution and their impact on the marine ecosystem and on fisheries are very poorly documented. As a consequence, fisheries impacts tend to be the ones more "visible" to the public. Because the fisheries sector is economically and socially weaker than the agricultural or industrial sector, there is a risk that governments and NGOs target it primarily when looking for short-term solutions to the growing environmental problem, raising the issue of intersectoral equity.

4.3 The Black Sea Example

The combined impacts from fisheries and land-based activities represent a very significant threat to aquatic ecosystems and to fisheries. The evolution of the Black Sea ecosystem provides an illustration of the problem. The freshwater input from land (346 km3 per year) is higher than the evaporation (323 km3 per year) and the bottom is covered with a stratum of anoxic salt water with a high methane and hydrogen sulphide content.

The Danube, Dniestr and Dniepr rivers carry to the Black Sea about 280 km3 of fresh water per year, representing 85% of the total input of fresh water into that sea. The watershed of the three rivers covers an area (1.4 million km2) that is 22 times larger than the Black Sea itself, and the Danube alone carries the waste water of 80 million people. At the end of the 1960s, the Black Sea was the most productive area of the Mediterranean, with a high diversity of pelagic and benthic fauna. After 1970, a very strong modification of the chemical and biological habitat occurred as a consequence of industrial development and intensive agriculture. Inputs of phosphorus and nitrate increased threefold and tenfold respectively while the input of silicate decreased fivefold. This resulted in a significant modification of the structure and functioning of the coastal ecosystem, including a change in dominance of the algal communities from diatoms to small- size dinoflagellates (Dinophysis spp.).

At the beginning these modifications appeared favourable for the ecosystem and fisheries. Phytoplankton production and copepod abundance increased and with them the abundance of plankton-feeding fishes. Fishing effort increased, leading initially to an increase in catches from 200 000 tonnes in 1970 to 600 000 tonnes in 1985 but resulting finally in overfishing. The ultimate consequence was an explosion of carnivore jellyfish (Aurelia aurita and Mnemiopsis leidy) consuming eggs and larvae and occupying the ecological niche formerly occupied by the small pelagic species depleted by overfishing The biomass of jellyfish increased from one million tonnes in 1970 to 700 million tonnes in 1985 (about 5 kg/m2). These jellyfish, having no predators, are a trophic "dead end", and their mortality generates an important bacterial activity and a large quantity of anoxic water near the bottom, reducing further the habitat for fishery resources (Bouvier, 1998).

4.4 Impact on Diadromous Fish

Diadromous fish, using both the inland and marine environments, illustrate the impact of non-fishery activities on fisheries. Habitat alteration, degradation and outright destruction by non-fishery activities are probably the primary cause of extinction in diadromous fishes (Jonsson et al., 1999). For example, among the diadromous species, the sturgeons are particularly threatened, with 13 of the 15 existing species being endangered, and restoration programmes and restocking will not lead to recovery unless the fundamental sources of decline (in addition to overexploitation), such as pollution and habitat degradation, are addressed (Jonsson et al., 1999). Many changes in fish stocks can be seen to result from changing of river runoff or influx of a layer of warm water (Mann, 1993). For example, the collapse of commercial snook fisheries in Florida during the 1950s has been attributed to habitat alteration and reduction of freshwater flow (Zerbi, 1999). Major environmental disturbances responsible for the decline of Salmo salar populations include the development of hydroelectric dams, which impede migration to spawning grounds, and acid rain, which degrades quality of nursery grounds. The poor state of Pacific salmon (Oncorhynchus spp.) is also a consequence of the economic development and exploitation of Northwest Pacific ecosystems, including trapping (furs), mining, timber harvesting, grazing, irrigation, dams, municipal and industrial development, pollution and excessive harvest (Lichatowich et al., 1999).

4.5 Competition Between Humans and Marine Mammals

Marine mammals are important predators located towards the apex of the oceanic food chain. They have been heavily depleted in the past and are still, in some cases, threatened with extinction. After decades of protection, many populations are again (or still) very abundant, and their feeding requirements place a very significant demand on ocean productivity. Some countries and stakeholder groups (see, for instance, are actively promoting the full protection of these species, questioning our capacity to establish a sustainable regime of exploitation. Other countries consider these species as essential resources and as competitors to humans, pointing to the very large quantities of fish consumed by them (Tamura, 2003).

4.6 Allocation Implications

Non-fishery impacts on resource abundance result in a reduction of the fishery resources available to humankind. While they may not be perceived as such by the fishery sector, they represent de facto a forced, non-negotiated, non-transparent, and potentially non-sustainable allocation of aquatic space and resources to non-fishing activities, often located far inshore (e.g. sources of pollution). One implication of the EAF is the need to deal with this problem in a more balanced and transparent way.

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