Download The effects of fisheries management practises on freshwater

Fisheries Management and Ecology, 2004, 11, 145–151
The effects of fisheries management practises on
freshwater ecosystems
I. G. COWX
University of Hull, International Fisheries Institute, Hull, UK
D. GERDEAUX
Station d Õhydrobiologie lacustre, INRA, Thonon cedex, France
Abstract The contributions presented at the European Inland Fisheries Advisory Commission Symposium on
The Effects of Fisheries Management Practises on Freshwater Ecosystems in 2002 are reviewed. The principal
mechanisms of inland fisheries management concentrate on four categories: fish stock enhancement (stocking and
introductions); rehabilitation and habitat manipulation for fisheries purposes, including biomanipulation; fisheries
regulations; and conservation and protection of fish and fisheries. The negative and beneficial impacts of these
activities are summarised and options for improving the outputs of fisheries management practices to accrue wider
benefits to society are discussed. Wider stakeholder participation and a shift from traditional fisheries towards
ecosystem-based management approaches are the main mechanism proposed. This calls for new management tools
to cater for legitimate human demand for water abstraction, hydropower generation and effluent disposal, as well
as alternative commercial use of water bodies such as bathing, boating and tourism, in addition to fisheries
exploitation and conservation needs.
biomanipulation, fish conservation, fish stock enhancement, fishery rehabilitation, inland fisheries management.
KEYWORDS:
Introduction
Inland fisheries are of high socio-economic and sociocultural importance, and provide Ôa myriad of benefits
to societyÕ (Weithman 1999; Welcomme & Naeve 2001;
Arlinghaus, Mehner & Cowx 2002). However, multipurpose use patterns, especially in industrialised
countries, have created a distinct climate for change
within the inland fisheries sector. Activities such as
agriculture, impoundment, channelisation, deforestation, navigation, wetland reclamation, urbanisation,
hydropower generation, water abstraction and transfer, and waste disposal have altered freshwater
ecosystems profoundly, probably more than terrestrial
ecosystems (Cowx 2002). As a result, the majority of
freshwater ecosystems in industrialised countries are
impacted and the fisheries heavily modified or degraded.
Recent trends in inland fisheries management have
attempted to address the problems created by societal
development to improve the aquatic environment for
biodiversity and allow for sustainable exploitation of
the resources (Arlinghaus et al. 2002). The principal
mechanisms of fisheries management concentrate on
four categories of action, each with distinct objectives.
These are: fish stock enhancement (stocking and
introductions); rehabilitation and habitat manipulation for fisheries purposes, including biomanipulation;
fisheries regulations; and conservation and protection
of fish and fisheries.
Despite these interventions little attention has been
paid to their overall impact on the aquatic ecosystem
in which they are enacted. This is a major knowledge
gap, particular with the shift in emphasis towards
ecosystem-based approaches to management of inland
waters (FAO 2003), where all stakeholders and
resources users should be involved in the decisionmaking processes so development in one sector does
not impact negatively on others. The problem is
exacerbated within Europe, because of the growing
Correspondence: Ian G. Cowx, University of Hull, International Fisheries Institute, Hull, HU6 7RX, UK
(e-mail: [email protected])
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pressure on European Union countries to improve the
status of rivers and lakes to meet their obligations
under the Water Framework Directive 2000/60/EC, as
well as the need to contribute towards protection of
biodiversity under the Habitats Directive 92/43/EEC.
Consequently, any activities that could potentially
have a detrimental impact on the ecosystem should be
avoided or mitigated against. In this context, the
European Inland Fisheries Advisory Commission
(EIFAC) recognised the need to improve understanding of the impacts of inland fisheries management
activities on the environment to meet the obligations of
the sector in a wider ecosystem-based approach to
management. To address this limitation the EIFAC
held a symposium entitled The effects of fisheries
management practises on freshwater ecosystems in
Windermere, UK, between 12 and 15 June 2002 with
the following objectives:
• to bring together inland fisheries experts to exchange
knowledge among countries and to appraise fisheries
management activities and their impact on the
environment, constraints on their application, issues
and options regarding their use, and the benefits and
problems associated with these activities;
• to identify constraints and gaps in knowledge
that affect the application of fisheries management
activities in inland fisheries;
• to recommend and promote action to improve the
management of inland fisheries to the benefit of the
aquatic environment; and
• to provide guidelines for the policy formulation,
planning methodology and evaluation of future
fisheries management activities.
This paper reviews the output of the EIFAC
symposium in the four principal areas of management
activities identified above and consolidates the information held within the proceedings that comprise this
issue of Fisheries Management and Ecology. Further
details of the output of the symposium can be found on
http://www.fao.org/docrep/005/y4261e/y4261e00.htm.
Impact of stocking and introductions on the
environment
Stocking and introduction of non-native species are
widespread management techniques used to improve
the quality and diversity of fisheries and enhance the
angling experience (Cowx 1994, 1998). They are also
used to manipulate population structures to influence
food webs with the ultimate goal of improving water
quality and ecosystem health (i.e. biomanipulation, see
later). However, these activities are achieved at considerable cost.
Some introductions and stocking programmes are
made illegally because recreational angling demand is
high and commercial benefits override the small fiscal
penalties incurred (Hickley & Chare 2004). It appears
that species-poor fish communities favour the establishment of non-native populations and are more
vulnerable to invaders because alien species are less
liable to be out-competed or predated upon by
indigenous species. Direct assessment of the impact
of introductions and stocking activities is seldom
possible but local increases in species richness and
abundance are likely to increase niche overlap, and
therefore inter- and intra-specific relationships are
more likely to be prevalent (van Zyll de Jong, Gibson
& Cowx 2004). Interactions could result from competition with indigenous fishes or direct predation on
native populations (Hickley & Chare 2004; van Zyll de
Jong et al. 2004; Winfield & Durie 2004). The genetic
effects of introductions and stocking are also considerable, and co-introduction of parasites has enabled
some diseases to become widespread in Europe
(Almodóvar & Nicola 2004; Hickley & Chare 2004;
van Zyll de Jong et al. 2004).
Despite these negative aspects, introductions and
stocking can also be successful because in some cases
the stocked species now support sustainable fisheries
with no detectable detrimental effects (Hickley &
Chare 2004). Consequently, fish introductions and
stocking should not be systematically assumed to be
negative, but risks appear to be higher with exotic
species than species translocated within an ecoregion
or the stocking of indigenous species. Unfortunately,
there is often insufficient information on impacts of
introductions and stocking programmes, particularly
because there is no systematic monitoring and dissemination of information on the outcomes. Causal
relationships are, therefore, difficult to distinguish
from indirect correlation with environmental parameters. It was recognised that managers have a dual role
in that they have to maintain, improve and develop
fishing at the same time as having to protect the
environment. Such a situation can lead to conflicts.
Nevertheless, the threats posed by fish stock enhancement programmes, especially introductions, are particularly insidious because recovery management tools
to overcome any adverse effects are not available. It is
therefore recommended that the precautionary
approach should be adopted with regard to the
introduction of species, particularly in the case of
non-native fishes. It is also recommended that international codes of practice are updated (e.g. ICES 1988
or EIFAC 1988) and followed to the letter to ensure
the risks associated with introducing fish or other
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EFFECTS OF FISHERIES MANAGEMENT ON FRESH WATERS
aquatic organisms are evaluated and the correct
decision to protect the extant biota is made. If
insufficient information is available to make a decision
on introducing a species, the precautionary principle
should be adopted and the enhancement exercise
curtailed.
It was also recognised that increasing scientific
understanding of fish and their habitat is required to
support legislation in this respect. Consequently, more
research is needed on the behaviour and mechanisms
involved in the spread of non-native species. There is
also a need for more information on the ecological
impacts of stocking, the economic valuation of inland
fisheries and the impact of introduced pathogens on
fish stocks. In this respect, the relative merits and cost
effectiveness of stocking rivers with different life stages
and at different times of the year could be useful in
determining if stocking contributes to improved stock
status (Aprahamian, Barnard & Farooqi 2004). For
example, when stocking rivers with fed salmon, Salmo
salar L., fry a net gain can be realised when natural
survival rates from egg to smolt are in the region of 1%
or less. At high survival rates in the wild, the advantage
of rearing and stocking fish is diminished. For coarse
fish, e.g. chub, Leuciscus cephalus (L.), dace, Leuciscus
leuciscus (L.) and roach, Rutilus rutilus (L.), stocking
either 1- or 2-year-old fish is unlikely to make a
significant difference to catches. In river rehabilitation
situations, where no population exists, stocking older
fish of >2 years old is likely to be more cost effective
and lead to faster establishment of self-sustaining
population, although knowledge of survival rates is
still lacking.
Rehabilitation of inland fisheries
Restoration of aquatic habitats towards pristine conditions is a utopian view (Cowx 2004). In most cases,
the watersheds have experienced extensive land-use
changes. The most dramatic impacts result from
deforestation, land use change, intensification of agricultural and industrial activity, and the modification of
river channels to control floods and provide for
navigation. More recently, demands for water resources and electricity have created new impacts. All
these changes have been superimposed upon environmental changes caused by recent global climatic
variations. The aim of rehabilitation for fisheries
should therefore be to recreate functional habitats
and connectivity between these habitats, and the target
should be a quality of environment that achieves a
compromise between maximum biodiversity and maximum productivity of fish. In this context, a functional
unit includes spawning, feeding, nursery (growth) and
resting (self protection) areas, each of which is linked
in various ways with environmental features.
Rehabilitation of rivers for fish focuses mainly on
reinstating lateral and longitudinal connectivity,
recreating habitat diversity and channel morphology,
improving flow regimes for fisheries purposes and
improving water quality problems (Cowx &
Welcomme 1998). In lowland floodplain areas, reconnection of backwaters and ponds, or connection of
adjacent gravel and borrow pits, which represent
valuable spawning and nursery habitats, have been
shown to increase species richness and relative
abundance of fishes, especially if coupled with controlled flooding of the floodplain habitat (Jurajda,
Ondračková & Reichard 2004). However, it appears
that rehabilitation activities often do not always meet
their desired objectives, partly because of lack of
understanding of the biotic and abiotic factors
influencing the target fish populations (Cowx 2004).
Also, rehabilitation schemes often fail to address wider
catchment problems and issues affecting fish communities, and/or manager’s expectations are too high.
There is thus a need to have an overview of the entire
catchment when establishing programmes for rehabilitation. Base line studies are needed to understand the
relative importance of imbalances in individual river
channels and tributary catchments relative to the
overall catchment. Such studies will identify bottlenecks to viable fish populations in the whole catchment, allowing the generation of habitat enhancement
procedures that will aid rehabilitation of a natural
balance. Unfortunately, activities that reduce the
impacts of development activities and resource extraction, which are an integral part of rehabilitation
measures, cannot be achieved by government intervention alone. Consequently, agency partnerships, as
well as legislation enforcement and compliance, are
necessary if rehabilitation exercises are to successful,
and greater emphasis must be given to providing
advice to clients, public education and outreach
activities to engender stakeholder participation in
conserving habitat (Goodchild 2004). Finally, it was
recognised that improvements achieved did not always
warrant the expense of the scheme, and better costbenefit analysis is required, including post-project
monitoring of rehabilitation works, if unsuccessful
schemes are not to be duplicated.
Rehabilitation of lakes largely focuses on shoreline
habitat improvements, reducing nutrient input and
overcoming the problems associated with eutrophication, including hypolimnic anoxia. Deep-water salmonid habitat can be expanded in lakes suffering from
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depleted summer oxygen levels by artificial mixing and
raising hypolimnic dissolved oxygen levels by oxygenation to at least 4–5 mg L)1, although the effects on
fisheries production are varied (Müller & Stadelmann
2004). This is largely because anoxic conditions, linked
to eutrophication, still persist if nutrient input to the
lake is not curtailed. In such cases the risk of fish kills
from toxic algae production persists, and sediments
continue to be anoxic causing mortality of whitefish
(Coregonus spp.) eggs (Müller & Stadelmann 2004).
Recruitment of fish populations can also be improved
through reinstatement of shoreline habitat diversity
and riparian and littoral zone vegetation (Jurajda et al.
2004). However, one tool that is being increasingly
used to overcome the problems with eutrophication
and to control algal blooms is biomanipulation.
Biomanipulation has been used in several regions of
Europe to control algal blooms, but with varying
degrees of success (Mehner, Arlinghaus, Berg, Dörner,
Jacobsen, Kasprzak, Koschel, Schulze, Skov, Wolter &
Wysujack 2004). Two main approaches are used:
(a) the traditional approach to biomanipulation by
enhancement of predators and reduction of
planktivorous fishes without participation of local
stakeholders and (b) approaches that consider the
socio-economic demands of anglers and commercial
fishermen, and biomanipulation conducted mainly by
means of the fishery.
Traditional approaches through manipulation of
density of piscivorous fish density and reduction of
planktivorous fishes are considered valuable tools for
reconciling fisheries and water quality problems on
lakes, although care is need to ensure that stocking
density of predators is adequate and appropriate
(Mehner et al. 2004). To assist in appropriate application of biomanipulation for lake rehabilitation,
Mehner et al. (2004) proposed step-by-step guidelines
that integrate all stakeholdersÕ interests. The guidelines
provide advice for water quality management but need
to be tested in practice, and the technological parameters have to be completed. The power of the approach
adopted within the guidelines lies in the integration of
traditional fisheries management measures, such as
stocking of piscivorous fishes, with ecosystem-based
management. Unfortunately, continuity of interventions still remains paramount for the long-term success
of biomanipulation activities. In this respect, anglers
and fishermen are an appropriate way of maintaining
continuous fishing pressure and should be used,
especially in countries with major commercial fisheries.
The use of experienced carp anglers in biomanipulation projects is recommended in cases where dense carp
stocks lead to a resurgence of eutrophication. In these
circumstances, catch and release should be avoided
(Mehner et al. 2004).
One source of nutrient input in fresh waters that
needs to be evaluated is anglersÕ groundbait. Bait seems
to be a substantial source of phosphorus in some
fisheries (Neisar, Arlinghaus, Rennart & Mehner
2004), although more experienced anglers are able to
maintain high catch rates without increasing the
amount of groundbait used. To alleviate this problem,
further investigations on phosphorus-reduced baits are
necessary and anglers should adopt methods that
reduce the amount of bait used. Furthermore, specific
management guidelines for ground- and pre-baiting
are needed because groundbaiting is generally common
among coarse fish anglers.
Fisheries regulations and stakeholder
involvement
Traditional fisheries management, through regulation
of fishing activities, can have positive benefits for fish
stocks. For example, in Lake Peipsi-Pihkva, problems
arise from differences in the species targeted by the
fisheries of Estonia and the Russian Federation, and
traditional technical measures to increase the selectivity and lower the efficiency fishing gears through larger
mesh-sizes, and imposing annual catch quotas have
successfully raised the catch potential of the stock to
cater for higher demand (Vetemaa, Vaino, Saat &
Kuldin 2001). Similarly, problems have been encountered with the overexploitation of the sturgeon fisheries
in the Lower Danube River, which are in a sate of
collapse and extinction of the species is a real threat
(Navodaru, Staras & Cernisencu 2001). The current
situation calls for classical remedies, including a
decrease of fishing effort, catch control and protection
of spawning areas, and enforcement of the regulations.
It is now recognised, however, that such traditional
approaches must be coupled with stakeholder involvement (Goodchild 2004). This is largely because there is
usually a lack of incentives when imposing traditional
fisheries management regulations, although the scientific knowledge for implementation of such management tools is available. For example, in Finland,
regulations restricting the movements of the alien
signal crayfish, Pacifactacus leniusculus Dana, to conserve the native crayfishes are often ignored because
the signal crayfish is resistant to crayfish plague,
Aphanomyces astaci Shikora, and has better growth
and reproduction potential than the native noble
crayfish, Astacus astacus L. (Kirjavainen & Sipponen
2004). Similarly, Irz, Arguillier & Proteau (2004)
showed that the practice of introducing non-native
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species in French reservoirs leads to lower species
richness and a reduction in species-biodiversity, but the
activity still persists. There is thus a need to change the
underlying thinking towards one that states that native
species per se are of higher value to society than
introduced or stocked non-native species. Similar
changes in philosophy against other fisheries management practices that have potentially negative effects are
also needed.
To this end, the democratic processes necessary to
protect and rehabilitate aquatic ecosystems, or fund
research programmes for protection of aquatic biodiversity, call for regulations that the fisheries sector
accept and follow. This goal will only be reached if the
incentives are either positive self-interest or a feeling of
collective moral and social obligations. Such an
approach was successfully applied in Finland, where
institutional changes have induced changes in fisheries
governance closely related to changes in society. Here,
the attitude towards the Saimaa ringed seal has
changed from that of a competitor to the fishermen
to one where the seals are perceived as part of a diverse
fauna in need of conservation (Tonder & Salmi 2004).
Effective fisheries management must therefore depend
on public support and very often the perception of
personal as against collective value trade-offs. This
change in perception of the importance of natural, as
well as artificial, water bodies, is slowly changing
traditional fisheries towards ecosystem-based management approaches. Ecosystem-based management systems represent a paradigm shift and may best be
described as adaptive management. This calls for new
management tools to cater for legitimate human
demand for water abstraction, hydropower generation
and effluent disposal, as well as alternative commercial
use of water bodies, such as bathing, boating and
tourism, in addition to fisheries exploitation and
conservation needs.
Role of fish conservation in environmental
management
Fresh waters have suffered the most intense intervention of all ecosystems over the past 100 years. As a
consequence, freshwater fishes have become threatened
by a wide array of factors, but anthropogenic disturbance, especially species introductions and translocations, impoundment of rivers, pollution, habitat
degradation and overexploitation, seems to underlie
the decline and extinction of many species (Cowx
2002). This has resulted in many fish species becoming
extinct, rare or endangered. Although actions have
been taken to address some precarious situations,
traditional methods of conservation management (e.g.
regulation of exploitation, designation of nature
reserves, captive breeding programmes for stock
enhancement) do not seem to be as effective for
freshwater fishes as for other animal groups (see
Collares-Pereira, Cowx & Coelho 2002 for examples).
This appears to be largely because fish populations and
communities are treated in isolation and do not adopt
a wider ecosystem-approach to conservation management. Traditional methods tend to concentrate on
protecting or enhancing localised populations and do
not necessarily address the bottlenecks contributing to
the population’s demise. In this context, the bottlenecks to recruitment and survival need identifying, and
mechanisms that overcome them should be put into
place if fish conservation management is to be
successful (Cowx & Collares-Pereira 2002). Strategies
for fish conservation management must therefore
adopt a more holistic approach accounting for other
stakeholder activities and actions within the catchment
and identify compromise scenarios that allow the
preservation of the targeted fish species, whilst allowing development of activities in other sectors. This
approach requires knowledge of biological, environmental, social and economic issues that affect the fish
and fisheries as well as other stakeholders. Only then
can compromise situations be formulated that benefit
all parts of society. Such an approach was illustrated
by Collares-Pereira & Cowx (2004), who reviewed the
present threats to freshwater fishes, identified the
underlying issues and reviewed the problems relating
to current management practices. They illustrated the
approach using a case study from a highly endangered Iberian cyprinid fish – Anaecypris hispanica
(Steindachner) – to highlight the options for action to
protect the freshwater fish natural heritage for future
generations. They concluded that if conducted in a
comprehensive manner, involving the wider public and
all stakeholders, fish conservation management will
confer wider environmental benefits, and protect
biodiversity for future generations. Ultimately, it
appears that fish conservation and improvement
actions can accrue wider environmental benefits and
help protect freshwater ecosystems from further degradation. This was illustrated by Noble, Harvey &
Cowx (2004), who showed that habitat management
activities to enhance fish population abundance can
have positive benefits for other biota. In this case,
rehabilitation of reedbeds to enhance fish population
structure and abundance was considered a major
factor enhancing the conservation status of the bitterns, Botaurus stellaris (L.), an extremely rare fisheating bird in the UK.
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Conclusions and recommendations
References
The Symposium highlighted that traditional inland
fisheries management has clear benefits to river and
lake ecosystems and to stakeholders over and above
benefits to the fishery itself, but it is not always
implemented successfully in European inland fisheries.
Furthermore, activities such as stocking and introduction of fish can have negative impacts. Recent paradigm
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The unwillingness of elements of the public to
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