The Department will ensure that wildlife and natural habitats are appropriately managed and effectively conserved for future generations, including coordinating and delivering action under the Isle of Man Government Biodiversity Strategy 2015-2025 and Biosphere Isle of Man. This dedication is in conjunction with the Convention on Biological Diversity. This convention is an international agreement to conserve and manage biodiversity, first signed in 1992 by 168 countries, including the UK.
In their natural state, rivers are heterogeneous habitats that provide for the differing needs of the various species and ages of native fish. For instance, young salmon prefer to occupy areas of shallow fast flowing water, with a moderately coarse substrate, while deep or slow moving water, particularly when associated with a sandy or silty substrate will not support juveniles. Also necessary for a healthy juvenile population are such features as surface turbulence, loose substrate, large rocks, undercut banks and overhanging and aquatic vegetation, which offer protection from predation and enable demarcation of territories. Such features also afford protection for mature resident and migratory fish. Adult salmon and sea trout also require deep, holding pools in which to rest on their upstream migration, especially immediately downstream from their spawning gravels.
Activities such as damming, dredging, riverbank engineering and channelisation can reduce the variety of physical habitat and, in some cases, result in sections of watercourses failing to cater for certain life stages of fish with consequential impact on the population as a whole. Obstacles to upstream migration, e.g. weirs, can cause under-utilisation of rivers and streams, and in some cases, extinction of diadromous fish within substantial stretches of suitable habitat. River habitat management aims to maintain appropriate natural variations in depth and river bed type (riffle, pool and glide), together with adequate cover and food production areas, and ensure that anthropogenic features have minimum impact on the ability of both resident and diadromous fish to migrate throughout the river network.
Activities such as flood management and commercial and non-commercial developments, may also exert a short or long term influence via temporary or permanent impacts on water quality, habitat quality and the ability of fish to migrate within rivers. The Fisheries Act 2012 introduced a number of legislative safeguards additional to those included in previous fisheries legislation. For instance, the requirement for the Department’s consent to be sought prior to extracting material from the bed of any watercourse has already succeeded in protecting areas of spawning habitat in some drainage ditches from the adverse impact that can result from maintenance being conducted during inappropriate periods.
The Inland Fisheries Section continue to promote the value of and need to conserve freshwater fish and their habitat to the wider public via distribution of information leaflets, e.g. Manx Watercourse Management Guide, and regular communication through conventional and social media. Inland Fisheries also promote and provide advice on good practice as regards river and riparian habitat management to other Government Directorates and Departments, and have built productive working relationships with several of the Island’s groundwork contractors, consulting engineers and architects. Inland Officers monitor, advise and comment on planning applications, where there is potential for the proposed development to have a temporary or permanent detrimental impact on river habitat and/or freshwater fish, such as improved passage for all freshwater fish species.
Fish Populations Under Threat
Localised extinction events such as the polluting of the Summerhill Glen caused by toxic substances being poured into surface water drains, have wider ranging environmental impacts over time. As more ‘small scale’ and ‘larger scale’ events occur, the totality of impact to the Island’s biodiversity leads to greater conservation issues. As an example, all aquatic life within the Glen was lost down to an impassable waterfall. The resident brown trout there had adapted to the microenvironment within the Glen potentially over hundreds of years, and their unique genetic variation was lost. It is recognised that fishery resilience relies on genetic variation within populations and each impact on this reduces the overall resilience of the species.
Enhancement stocking of Atlantic salmon, aiming to boost adult returns for anglers by boosting the juvenile population to above the natural carrying capacity, has generally been regarded as ineffective and potentially counter-productive as a means of conserving a natural fishery. There are however circumstances where stocking can be beneficial (as recognised by the Atlantic Salmon Trust), only for the purposes of mitigation or restoration. The Inland Fisheries restocking programme has aimed to assist depleted local populations and monitoring has indicated that stocking has been successful in substantially boosting juvenile recruitment in several locations.
Recreational Fishing Restrictions
The Fisheries Act 2012 provides the primary legislation for the protection of Manx freshwater fish stocks, including migratory salmonids (Atlantic salmon and sea trout) in coastal waters.
Commercial fishing and angling activities involve the exploitation of fish stocks and can pose a wide range of potential impacts on both the density and composition of fish populations. Legislation regulates the ways in which both commercial fishing and recreational angling can be pursued and how fisheries can be managed legitimately. In order to ensure the successful protection of freshwater fish populations, there must be effective regulation and enforcement of the appropriate legislation. On the Isle of Man, fisheries enforcement activities are carried out on both coastal and inland waters. The work can be labour-intensive and costly, and therefore must be carefully prioritised and planned to ensure a high degree of effectiveness.
Fishing restrictions and legislation encourage participation in river angling on the Isle of Man, without compromising the sustainability of the native fish populations.