Overcoming the dichotomy of implementing societal flood risk management while conserving instream fish habitat - A long-term study from a highly modified urban river.

Flood Risk Management (FRM) is often essential to reduce the risk of flooding to properties and infrastructure in urban landscapes, but typically degrades the habitats required by many aquatic animals for foraging, refuge and reproduction. This conflict between flood risk management and biodiversity is driven by conflicting directives, such as the EU Floods and Water Framework Directives, and has led to a requirement for synergistic solutions for FRM that integrate river restoration actions. Unfortunately, ecological monitoring and appraisal of combined FRM and river restoration works is inadequate. This paper uses a case study from the River Don in Northern England to evaluate the effects of the FRM and subsequent river restoration works on instream habitat and the associated fish assemblage over an 8-year period. Flood risk management created a homogeneous channel but did not negatively affect fish species composition or densities, specifically brown trout. Densities of adult brown trout were comparable pre and post-FRM, while densities of juvenile bullhead and brown trout increased dramatically post FRM. River restoration works created a heterogeneous channel but did not significantly improve species composition or brown trout density. Species composition post-river restoration works returned to that similar to pre-FRM over a short-term period, but with improved numbers of juvenile bullhead. Although habitat complexity increased after river restoration works, long-term changes in species composition and densities were marginal, probably because the river reset habitat complexity within the time framework of the study.

Development and application of a machine learning algorithm for classification of elasmobranch behaviour from accelerometry data.

Discerning behaviours of free-ranging animals allows for quantification of their activity budget, providing important insight into ecology. Over recent years, accelerometers have been used to unveil the cryptic lives of animals. The increased ability of accelerometers to store large quantities of high resolution data has prompted a need for automated behavioural classification. We assessed the performance of several machine learning (ML) classifiers to discern five behaviours performed by accelerometer-equipped juvenile lemon sharks (Negaprion brevirostris) at Bimini, Bahamas (25°44'N, 79°16'W). The sharks were observed to exhibit chafing, burst swimming, headshaking, resting and swimming in a semi-captive environment and these observations were used to ground-truth data for ML training and testing. ML methods included logistic regression, an artificial neural network, two random forest models, a gradient boosting model and a voting ensemble (VE) model, which combined the predictions of all other (base) models to improve classifier performance. The macro-averaged F-measure, an indicator of classifier performance, showed that the VE model improved overall classification (F-measure 0.88) above the strongest base learner model, gradient boosting (0.86). To test whether the VE model provided biologically meaningful results when applied to accelerometer data obtained from wild sharks, we investigated headshaking behaviour, as a proxy for prey capture, in relation to the variables: time of day, tidal phase and season. All variables were significant in predicting prey capture, with predations most likely to occur during early evening and less frequently during the dry season and high tides. These findings support previous hypotheses from sporadic visual observations.

Diel variations in the assemblage structure and foraging ecology of larval and 0+ year juvenile fishes in a man-made floodplain waterbody.

This study investigated diel variations in zooplankton composition and abundance, and the species composition, density, size structure, feeding activity, diet composition and prey selection of larval and 0+ year juvenile fishes in the littoral of a man-made floodplain waterbody over five 24 h periods within a 57 day period. There was a significant difference in the species composition of diurnal and nocturnal catches, with most species consistently peaking in abundance either during daylight or at night, reflecting their main activity period. There were no consistent diel patterns in assemblage structure or the abundance of some species, however, most likely, respectively, due to the phenology of fish hatching and ontogenetic shifts in diel behaviour or habitat use. There were few clear diel patterns in the diet composition or prey selection of larval and 0+ year juvenile roach Rutilus rutilus and perch Perca fluviatilis, with most taxa consistently selected or avoided irrespective of the time of day or night, and no obvious shift between planktonic and benthic food sources, but dietary overlap suggested that interspecific interactions were probably strongest at night. It is essential that sampling programmes account for the diel ecology of the target species, as diurnal surveys alone could produce inaccurate assessments of resource use. The relative lack of consistent diel patterns in this study suggests that multiple 24 h surveys are required in late spring and early summer to provide accurate assessments of 0+ year fish assemblage structure and foraging ecology.

The behaviour and recovery of juvenile lemon sharks Negaprion brevirostris in response to external accelerometer tag attachment.

Behavioural responses of lemon sharks Negaprion brevirostris to a fin-mounted tag package (CEFAS G6A tri-axial accelerometer with epoxied Sonotronics PT4 acoustic transmitter) were measured in a controlled captive environment (n = 10, total length, LT range 80-140 cm) and in free-ranging sharks upon release (n = 7, LT range 100-160 cm). No changes were detected in behaviour (i.e. swimming speed, tailbeat frequency, time spent resting and frequency of chafing) between control and tagged captive shark trials, suggesting that the tag package itself does not alter behaviour. In the free-ranging trials, an initial period of elevated swimming activity was found in all individuals (represented by overall dynamic body acceleration). Negaprion brevirostris, however, appeared to recover quickly, returning to a steady swimming state between 2 and 35 min after release. Post-release tracking found that all sharks swim immediately for the shoreline and remain within 100 m of shore for prolonged periods. Hence, although N. brevirostris are capable of quick adaptation to stressors and demonstrate rapid recovery in terms of activity, tracking data suggest that they may modify their spatial use patterns post release. This research is important in separating deviation in behaviour due to environmental stressors from artefacts caused by experimental techniques.

Managing conflicts arising from fisheries enhancements based on non-native fishes in southern Africa.

Southern Africa has a long history of non-native fish introductions for the enhancement of recreational and commercial fisheries, due to a perceived lack of suitable native species. This has resulted in some important inland fisheries being based on non-native fishes. Regionally, these introductions are predominantly not benign, and non-native fishes are considered one of the main threats to aquatic biodiversity because they affect native biota through predation, competition, habitat alteration, disease transfer and hybridization. To achieve national policy objectives of economic development, food security and poverty eradication, countries are increasingly looking towards inland fisheries as vehicles for development. As a result, conflicts have developed between economic and conservation objectives. In South Africa, as is the case for other invasive biota, the control and management of non-native fishes is included in the National Environmental Management: Biodiversity Act. Implementation measures include import and movement controls and, more recently, non-native fish eradication in conservation priority areas. Management actions are, however, complicated because many non-native fishes are important components in recreational and subsistence fisheries that contribute towards regional economies and food security. In other southern African countries, little attention has focussed on issues and management of non-native fishes, and this is cause for concern. This paper provides an overview of introductions, impacts and fisheries in southern Africa with emphasis on existing and evolving legislation, conflicts, implementation strategies and the sometimes innovative approaches that have been used to prioritize conservation areas and manage non-native fishes.

Failure to engage the public in issues related to inland fishes and fisheries: strategies for building public and political will to promote meaningful conservation.

Generating awareness of environmental conservation issues among the public is essential if there is an expectation of them to alter their behaviour, facilitate informed decisions and engage governments or regulatory authorities to take action. There are, however, exceedingly few public engagement success stories related to inland fishes and fisheries policy and resource allocation decisions. Inland aquatic resources and their associated fisheries provide employment, recreation, culture and, in developing regions, a considerable proportion of human nutrition and food security. Freshwater fishes are incredibly diverse but are among the most endangered organisms globally. Many threats to inland fisheries are driven largely by externalities to inland fisheries. The purpose of this paper is to draw attention to the role and plight of inland fishes and fisheries, and the need to generate the public and political will necessary to promote meaningful conservation. With this paper, the extent to which the scientific and environmental management communities have failed to engage the public in issues related to inland fishes and fisheries is characterized. Next, the barriers or factors that serve as the basis for the problem with public engagement are identified. The paper concludes by identifying strategies, including those focused on environmental education initiatives, for building the public and political will necessary to promote meaningful conservation of inland fishes and fisheries in developed and developing countries. Scientists, environmental managers, non-governmental organizations, politicians, regulatory authorities and the media all have important roles to play in overcoming challenges to inland fisheries. Failure to engage the public in freshwater conservation and management issues will impede efforts to stem the loss of freshwater habitats, fisheries and aquatic biodiversity. Thankfully, there are opportunities to learn from success stories related to other environmental issues and initiatives that have been successful in marine fish conservation.

Restoring river connectivity: prioritizing passage improvements for diadromous fishes and lampreys.

Physical obstructions are becoming increasingly recognized as major factors influencing the migrations, population structures, spawning success and recruitment of freshwater organisms. This paper presents a simple but effective method, intended for use by environmental managers, government agencies and conservation bodies, of rapidly assessing and prioritizing barriers to the migrations of diadromous fishes and lampreys for passage improvements. A prioritization matrix was developed using information on fish stock status, the passage efficiency of fishes at individual structures, the distance from the tidal limit and the passability of downstream barriers, and the quantity and quality of habitat upstream of each structure. Importantly, the 'Likelihood of access' was incorporated into the matrix to account for passage efficiency at downstream barriers. Barriers ranked as the highest priority for passage improvements were those characterized by poor fish stocks upstream, low passage efficiency, easy passage from downstream, and a large quantity and high quality of habitat upstream. Prioritization of migration barriers should ensure that access improvements are targeted to achieve optimum benefits.

Paradigm shifts in fish conservation: moving to the ecosystem services concept.

Various factors constrain the existence and development of inland fishes and fisheries, such as pollution, habitat degradation, alien invasive species, local user conflicts, low social priority and inadequate research and funding. In many cases, however, degradation of the environment and loss of aquatic habitat are the predominant concerns for the conservation of freshwater aquatic biota. The need for concerted effort to prevent and reduce environmental degradation, as well as protection of freshwater fishes and fisheries as renewable common pool resources or entities in their own right, are the greatest challenges facing the conservation of fishes in inland waters. Unfortunately, traditional conservation practices such as regulation of exploitation, protected areas and habitat restoration have failed to arrest the alarming increase in number of threatened freshwater fish species worldwide. This paper examines the shifting paradigm of fisheries management from rule-based regulation, through fishery enhancement towards the ecosystem approach to fisheries, with reference to inland waters, and how the emerging concept of ecosystem services coupled with traditional fish conservation management practices, institutional restructuring and integrated management planning should provide a more sustainable thrust to formulation and promotion of fish conservation initiatives.

Is there evidence for a shift in fish growth and recruitment success linked to climate change?

This study investigated whether a putative shift in climate regime in the North Atlantic in the 1990s coincided with changes in the growth and recruitment of roach Rutilus rutilus in the north-east of England. The relationships between R. rutilus growth and recruitment and the environment were significantly different before and after the putative shift in climate regime. Water temperature, river discharge, growth, recruitment success and the Gulf Stream Index co-varied until the late 1990s, indicating a gradual progression between periods of warm-and-dry and cold-and-wet summers. Since the late 1990s, there has been an increased prevalence of warm-and-wet summers, and recruitment success has oscillated between extremes on an almost annual basis. The north wall (northern boundary) of the Gulf Stream has been undergoing a displacement south since the late 1990s, and the speed and amplitude of the change appears to support the hypothesis that there was a regime shift in the climate of the North Atlantic Ocean. It is possible that a continued displacement south of the north wall of the Gulf Stream will lead to further increases in river discharge, reductions in water temperature and reduced fish growth and recruitment success in the long term.

Harmonizing recreational fisheries and conservation objectives for aquatic biodiversity in inland waters.

The importance of recreational fisheries to local and national economies, and as a generator of immense social welfare throughout the developed world, is well established. Development in the sector and its interaction with non-fishery-related nature conservation objectives for aquatic biodiversity, however, have the potential to generate conflict. This article reviews the intersection between recreational fisheries and nature conservation goals for aquatic biodiversity with specific reference to inland waters in industrialized countries, and the principal management activities and constraints that can lead to conflicts. A SWOT (strengths, weaknesses, opportunities and threats) analysis was used to review the issues facing sectoral development and identify options for future advancement of recreational fisheries to ameliorate potential conflicts with nature conservation goals. It is concluded that reconciliation of recreational fisheries and modern conservation perspectives is both possible and desirable, because many conservation problems also benefit fisheries quality. Angler buy-in to conservation is probable if (1) management scales are small, (2) threats to conservation originate from outside the fisheries sectors and (3) ecological awareness for the conservation problem is high. If these aspects are not present, reconciliation of recreational fisheries and nature conservation goals is less likely, risking both the aquatic biodiversity and the future of angling. To address these issues, enforcement of legislation and continued communication with angler communities is necessary, as well as development of integrated management policies that build on the instrumental values of aquatic biodiversity for recreational fisheries, while curtailing the more insidious threats to such biodiversity that originate directly from the recreational fisheries sector.

Dispersal and survival of stocked cyprinids in a small English river: comparison with wild fishes using a multi-method approach.

Mark-recapture and fixed-station passive integrated transponder (PIT) telemetry were used to compare movements, distribution and survival of stocked juvenile chub Leuciscus cephalus and roach Rutilus rutilus with those of wild conspecifics. Daily activity of wild fish activity was affected by a combination of river flow and temperature, whereas stocked fishes were not influenced by environmental factors. PIT telemetry recorded exploratory movements of stocked L. cephalus immediately after stocking, a substantial number of stocked fish moved both downstream and upstream during periods of elevated flow, and proportionally more stocked fish moved during the first 6 weeks after release than later on. Proportionally more stocked fish than wild fish moved through PIT antennae, stocked L. cephalus moved greater distances than wild L. cephalus and were more widely distributed than wild fish. Minimum estimates of survival after 5 months were 50.5% for stocked R. rutilus and 28.0% for stocked L. cephalus. Ultimately, stocked cyprinids appeared to be able to cope with elevated flows and most remained in the river section local to the stocking location.

Contrasting pragmatic and suffering-centred approaches to fish welfare in recreational angling.

Two views dealing with fish welfare in recreational fishing are discussed in an effort to stimulate the current discourse on the topic. The pragmatic approach asks whether and how strongly recreational fishing compromises the health and fitness of individual fishes and what can be done to avoid or mitigate such effects. Its implementation rests on accepting recreational fishing as a principally legitimate activity. The second approach to fish welfare focuses on suffering and pain in fishes and is usually morally prescriptive. Its central tenet is that some or all recreational fishing practices may be unacceptable unless sufficient benefits to humans are created, which justify the supposedly cruel treatment of the fishes. The pragmatic approach to fish welfare is preferred because it relies on objectively measurable variables of impaired fish welfare (e.g. physiological, behavioural or fitness indicators) and does not question recreational fishing on moral grounds. Contrary to a suffering-centred approach to fish welfare, a pragmatic perspective emphasizes positive messages and facilitates constructive dialogue among stakeholders. In contrast, a suffering-centred approach to fish welfare tends to promote tension and enduring conflict that cannot be reconciled objectively and thus should be avoided.

Response of the fish populations of the River Don in South Yorkshire to water quality and habitat improvements.

The River Don in Yorkshire, UK, has suffered a legacy of pollution and land contamination that dates back to the Industrial Revolution. The river continues to be impacted by discharges from industry, mining and sewage sources, resulting in poor water quality and considerable damage to the fish stocks. Some modest reductions in ammonia, biochemical oxygen demand (BOD) and metal levels have been achieved through improvements to sewage treatment works and the shutting down of some industries. The decline in the steel industry has generally led to sustained low and acceptable levels of iron and nickel in the river, although some locations are impacted by ochre from abandoned mines. As a consequence, recreational fishing in the catchment remains restricted at many locations. Fish stocking and enhancement programmes have so far been ineffective due to setbacks from ad hoc pollution incidents and degraded habitats. It is suggested that the water quality and habitat degradation problems be addressed prior to embarking on any large-scale fish stock enhancement programmes. This would require substantial financial investment and it is recommended that funding be actively sought from both internal and external agencies to achieve this objective.