Mariculture & Fishing
Human use of living marine resources provides a wide range of goods and services of economic value to OSPAR countries. However, these uses exert pressure on the coastal and offshore environment which can have a wide range of impacts on marine ecosystems. Use of living marine resources covers the exploitation of marine species by man for food, feed, fertilizer or the production of other products of value or use, and includes activities such as fishing, mariculture and hunting. These activities are of high economic significance in some OSPAR countries and in some regions within countries.
OSPAR’s Biodiversity and Ecosystems Strategy addresses both the protection of species, habitats and ecosystem processes and the management of human uses of the sea. The Strategy includes the following actions:
- Assessment of the impact of human activities on the marine environment.
- Drawing up of programmes and measures for controlling human activities that have an adverse impact on species and habitats that need to be protected and conserved, where this is necessary.
- Drawing the attention of fisheries management authorities to questions where OSPAR considers that action is desirable. For this purpose, OSPAR considers the management of fisheries to include management of marine mammals.
Mariculture in the OSPAR area
Mariculture is the cultivation of marine organisms such as fish and shellfish for food and other products. In 2006, almost 1.5 million tonnes of farmed fish and shellfish were produced in the OSPAR area representing 4.2% of world mariculture production. Since 1998, production of finfish in the OSPAR area has increased by 57% mainly due to increased production in Regions I and II. Shellfish farming, which is most intensive to the south of Region II and in Region IV, remained stable over the same period.
There are many concerns linked to mariculture, both in relation to rearing practices and to the widespread exchange and movement of eggs, embryos and seed, especially when different eco-regions are involved. Examples of these concerns include genetic interaction between farmed fish and wild stocks, transfer of parasites and diseases, spread of non-indigenous species, and dependence on industrial catches of wild fish to feed fish in mariculture. There are also concerns over a number of site-specific impacts from mariculture facilities, including:
- Eutrophication as a result of nutrient enrichment from feeds and effluents.
- Competition between escaped farmed fish and wild stocks for spawning grounds in freshwater habitats.
- Release of chemicals used to prevent fouling of equipment or to treat parasites and diseases.
- Displacement of bird and seal populations as a result of the use of scaring devices to discourage predation of farmed fish.
- Impacts from the harvesting of shellfish and from seed collection for mussel farming.
Measures are in place to reduce impacts of mariculture
OSPAR recommends best environmental practice (BEP) to reduce inputs of potentially toxic chemicals from aquaculture use. In addition, measures under OSPAR’s Eutrophication, Hazardous Substances and Biodiversity and Ecosystems Strategies provide a means to monitor, assess and regulate the impacts of mariculture. Various national and EU measures address the pollution and biodiversity impacts of mariculture. There are also international risk assessment protocols developed by ICES for assessing the risks of using non-indigenous species in aquaculture.
Use of hazardous substances has been reduced in mariculture
Although OSPAR’s recommendations on BEP for the reduction of inputs of potentially toxic chemicals from aquaculture use are not fully implemented in national legislation, the aims do seem to have been taken up by national or EU legislation. Increased use and development of vaccines has considerably reduced the application of antibiotics in mariculture. Tributyltin (TBT) in anti-fouling agents for mariculture equipment has been replaced by copper-based substances. Concern has been raised about possible increases in the release of copper, especially in Regions I and II. It is likely, however, that apparent increases are actually an artefact of better monitoring and reporting and that the actual usage of copper may have even reduced.
Effects of mariculture on wild populations need better understanding
Lice from farmed salmon have been linked to the decline in wild salmon and sea trout near salmon farms, but further evidence is needed to make a direct association. In 2007, the contribution of escaped salmon from mariculture to national catches in the North-East Atlantic was around 15% in Norway, but less than 2% in most other OSPAR countries. The main risks associated with escape of farmed fish are the displacement of wild fish and genetic interactions. An expansion of mariculture with a focus on carnivorous fish species is likely to increase demand for feed derived from industrial fishing of wild stocks. These issues show the need for a better understanding of interactions between fish farming and wild fish stocks.
Climate change may increase introduction of non-indigenous species
Increased sea temperatures have the potential to change the areas where introduced species can become established. Pacific oysters, introduced into the OSPAR area as a mariculture species, have established wild populations in France and as far north as Denmark and Sweden – areas previously thought too cold for them to reproduce. These introductions can lead to displacement of indigenous species with consequences for associated fauna.
Wider impacts of mariculture should be kept under review
Mariculture activities are very diverse and impacts are site-specific. Regulation and control therefore need to be focused on a case-by-case approach. OSPAR countries continue to implement the measures that are already in place to mitigate impacts from mariculture. OSPAR needs to keep under review the wider impacts, such as non-indigenous species, impacts of sea lice, escaped fish and increased demand for industrial fisheries, especially in the event of substantial increases in mariculture activities. If necessary, coordinated management may then be required. The need to adapt mariculture management approaches to climate change should also be reviewed.
Fisheries in the OSPAR area are regulated through a combination of different arrangements. These include national policies and regulations, the EU Common Fisheries Policy, bilateral and multilateral agreements between countries with shared stocks, and measures adopted by the three regional fisheries management organisations: the North East Atlantic Fisheries Commission (NEAFC), the International Commission for Conservation of Atlantic Tunas (ICCAT), and the North Atlantic Salmon Conservation Organization (NASCO).
OSPAR & Fisheries Regulation
The OSPAR Convention fully recognises the competence of these authorities to regulate fisheries. OSPAR informs these fisheries authorities when it considers that there are questions where action is needed to protect and conserve the North-East Atlantic in relation to fisheries. To facilitate this process OSPAR has adopted memorandum of understanding with both NEAFC and NASCO that detail their roles in conserving marine biodiversity within their respective mandates.
Direct and indirect effects of fishing
Fisheries have a range of direct and indirect effects on marine ecosystems. Fishing causes the death of many species including those being targeted and a range of other species such as non-targeted invertebrates and fish (including sharks), seabirds, turtles and marine mammals (seals and small cetaceans) through bycatch. Excessive fishing pressure on targeted species may lead to impaired reproductive capacity and a risk of stock collapse. Deep-water species have been shown to be particularly sensitive to fishing pressure. Discards have been shown to affect the structure of biological communities, however the new Common Fisheries Policy does away with the wasteful practice through the introduction of a landing obligation, which will be introduced gradually, between 2015 and 2019 for all commercial fisheries.
Certain types of fishing gear physically disturb or damage the seabed and so affect benthic habitats and communities, including those which OSPAR has listed as threatened and/or declining, such as seamounts and cold-water coral reefs.
Fishing causes changes in community structure and marine food webs, which may be irreversible. The depletion of larger predatory species has strong effects on fish community structure. Recent research has shown that impacts from fishing on the abundance of fish can be transmitted into deep offshore areas below the maximum depth of commercial operations. While certain impacts of fishing are inevitable, one long-standing challenge of sustainable fisheries management is to minimise long-term negative effects on ecosystems while seeking long-term economic and social viability of the fisheries.
Fishing may increase the vulnerability of ecosystems
Fish stocks are an integral part of ecosystems and, as such, are both strongly dependent on, and support, the good health of the ecosystem. Altered community structure and marine food webs therefore affect commercial fish stocks, particularly during periods of environmental change. In combination with other environmental impacts, such as pollution, climate change and ocean acidification, the effects of fishing may increase the vulnerability of ecosystems.
Assessment of the impact of bottom trawling
One of the main human activities that impact upon the marine environment is fisheries, and whilst OSPAR doesn’t have a mandate for fisheries management it does have a responsibility to assess the environmental effects of fisheries on the marine ecosystem.
Therefore in 2013 OSPAR decided for the first time to map the bottom fishing intensity in the North-East Atlantic. The purpose was to provide an input both to the assessment of seafloor integrity and physical damage and to assess the extent of fisheries impacts so they could be included in cumulative effects assessments.
Therefore OSPAR requested ICES to prepare a first OSPAR-wide mapping of the spatial and temporal intensity of fishing activities with mobile bottom contacting gears. To develop the maps ICES issued a data call to all Contracting Parties for national VMS and log book data. The analysis anonymised the data to ensure that individual vessels could not be identified and the spatial analysis of bottom fishing (towed gears) used VMS and logbook data to map activity at the resolution of 0.05 × 0.05 degree grid cells. Therefore the maps of bottom fishing intensity represent the number of times each unit of seabed has been trawled per year.
The analysis looked at four different gear types: beam trawls, demersal seines, dredges, and otter trawls and undertook two types of mapping: Fishing Effort and Fishing Intensity.
The effort maps contain the sum of all relevant fishing activities in an area, including all relevant fleets. ICES considered beam trawls, demersal seines, dredges, and otter trawls as towed bottom gears.
Fishing intensity (swept area ratio) required information on gear width and fishing speeds. These features differ for each gear, method of use, and target species (‘métier’). Mapping of the sum of the intensity of all métiers (km2) per grid cell, where possible, include the upper and lower estimates of the swept area to take account of uncertainties in defining fishing activity and gear widths and of missing effort.
Outlined below are two examples of output maps: figure 1 is the fishing effort for Otter trawls from 2009-2012 and figure 2 is the fishing intensity for 2009-2012 combined for Otter trawls, beam trawls and Dredges.
Fishing effort is clearly not uniformly distributed in the OSPAR area. Beam trawls are used in shallower waters (< 100 m depth) with beam trawling for shrimp, for example, in nearshore waters less than 20 m in depth. Demersal seines are very patchy in their use. Dredges are used offshore solely for scallops and nearshore use of dredges for blue mussels and oysters can be seen in some years. Otter trawl (Figure 1) is the most widely used towed gear, but high intensity use is confined to a small proportion of the area, with highest use in areas where Nephrops or Pandalus are targeted. The overall pattern of fishing was relatively consistent over the period, particularly in relation to the areas of higher fishing effort.
Fishing intensity (surface + subsurface) for OT, TBB, and DRB gears (see Annex 220.127.116.11 for codes) combined for the years 2009–2012. The colour in each 0.05 × 0.05 degree grid cell corresponds to the swept area ratio (average number of times fished per year).
Moving from intensity to impact
Although maps of the fishing intensity will reveal the seabed areas that are most heavily fished, these maps do not necessarily show which areas are impacted most heavily. Trawling impact is a combination of trawling intensity (frequency at which the seabed is being trawled by year), the depth of penetration, and the sensitivity of the seabed habitat. Further work is required to provide a consistent classification of the sensitivity of seabed habitats to overlay with the trawling intensity maps by gear type.