Potential Impacts of Climate Change on Artisanal Fisheries of Nigeria

Climate change (CC) refers to a change in the state of the climate that can be identified by changes in the mean and/or the variability of its properties, and that persists for an extended period, typically decades or longer. It refers to any change in climate over time, whether due to natural variability or as a result of human activity [1]. Artisanal fisheries is a traditional fisheries for subsistence or commercial fishing using traditional or small scale fishing gears (nets, traps etc) and motorized or unmotorized vessels (dugout boats and canoes). Artisanal fishermen use relatively small amount of capital and energy for fishing activities, and the fishing trips are often short or none at all close to the shore, while the fish caught are sold locally or consumed by the household. Artisanal fisheries contribute about 30% of GDP of developing countries, while 5% of the population about 35 million people depends wholly or partly on fisheries sector for their livelihood [2]. At present, in Nigeria, fish production by artisanal fishers dominates fish production in Nigeria contributing about 85% of fish production, since aquaculture that could compliment the fisheries is not well developed.

Climate change will have impact on aquatic ecosystems through many direct and indirect ways. Capture fisheries which is the base of artisanal fisheries is tightly linked with aquatic ecosystem processes and thus any change in the ecosystem processes will certainly pose serious negative impacts on artisanal fisheries of sub-Saharan Africa with great danger to sustainable livelihood of the people, socio-economic characteristics of the fisher folks and undermining the desirability of the region attaining the millennium development goals by 2015. Nigeria is vulnerable to the potential negative impacts of climate change through the rise in annual mean temperature, declining rainfall, increasing frequency and intensity of floods, and changes in rainfall seasons. All these will contribute to negative impacts of artisanal fisheries of the country.

The primary cause of CC in freshwater ecosystems is global warming. Gas flaring in the Niger delta region of Nigeria could be responsible for the increase in temperature and the associated global warming scenarios in Nigeria freshwater ecosystems. This is becoming evident from the episodic events in the frequency and intensity of rainfall, flooding, drought, rise in temperature, low flow of rivers, decrease in run-off and other associated climatic changes manifesting in different parts of the country (Figures 1 and 2). BNRCC [3] has projected increases in maximum daily temperature across Nigeria. Nigeria is more vulnerable to climate change because of the low-lying nature of about 800 km of coastline. Barrange and Perry [4] noted that warming in Africa is likely to be larger than global annual mean warming in all seasons with drier sub tropics warming more than the wetter tropics and rainfall will likely decrease. Predictions suggest that negative impacts will be felt across 25% of Africa inland aquatic ecosystem by 2100 affecting water quantity, quality resources and uses [5]. Bates et al. [6] also concluded that freshwater resources are highly vulnerable and have the greatest potential to be strongly impacted by climate change.

Figure 1: Map of Nigeria showing the States where artisanal fisheries take place.

Figure 2: Effect of annual variations in temperature in Southern Nigeria over time.

Fish are often the greatest target of CC as increasing temperature tends to affect every stage of their life cycle from their physiological, morphological, reproductive, migratory and behavioural responses. Alterations in their food-web processes and interactions, species invasion and spread of vector-borne diseases could also result from the effects of CC. Rosenzneig [7] reported that surface water temperatures have warmed by 0.2 to 2°C in lakes of Europe , North America and Asia with stratified periods advanced by up to 20 days and lengthened by 2-3 weeks. This is also true in Africa as a result of increasing gas emissions. Since fish are cold blooded, they are very sensitive to temperature changes. Any increase in temperature above the tolerance limit in their habitat will surely have serious negative effects on fish physiology especially in the supply of oxygen to their tissues. CC will impact on the spawning success of fishes spatially and temporally. This is because time and locations of spawning of several species of fish are linked to physical conditions such as temperature, currents etc, as well as biological factors like food. Changes in these conditions on account of CC would therefore impact negatively on the spawning of fishes in these habitats. Likewise, food and feeding of fish would be affected as plankton production in aquatic ecosystem is linked to physicochemical variables of the ecosystem which could be seriously affected by change in the climate. Delayed or prolonged hydrographic events such as increase temperature affect primary production and subsequently could jeopardize food web processes in lakes. Thus, a shift in food and feeding could result in the system as a result of CC. For instance high predation rate might occur on larvae if food production decreases. This will in turn affect the recruitment of fish species and their population in such environment. Global warming has been implicated in driving away fish species from their home range with likelihood of extirpating the population. O’Reilly [8] linked decline of fish abundance to climate impacts on Lake Ecosystem in the East African Rift Valley lakes, thus bringing about a change in the pelagic fisheries of the lake. Parmesan and Yohe [9] have reported that measurable changes in the phenologies and/or distribution of freshwater fish species will occur due to climate change. This might be possible due to increasing temperature in lakes and rivers which might bring disruptions and distortions in the phenology and seasonal fluctuations and assemblages of fish species and their food (plankton). Another possible effect of global warming in lakes is species invasions and diseases outbreak [10]. Climate change could be a predisposing factor for the new emerging diseases in fish through dispersal, migration or shift in the distribution of hosts or pathogens. Positive correlations have been found between increase temperature and pathogen manifestation, survival, development, transmission and host vulnerability [10]. Massive mortalities of Moroccan sardines in 1997 were linked to abrupt environmental changes [4]. CC could also facilitate the establishment and spread of deliberately or accidentally introduced genetically modified fish, through the provision of favourable environment factors such as increase in temperature of the water as well making the native species to be resistant to the invading species [11]. Algal successions in lakes could be impacted through global warming which may lead to the development of harmful algal blooms (HAB). Edwards et al. [12] has reported this scenario in North East Atlantic.

Any effect of CC produced on fish and its habitat will affect the fisheries and the fishermen, since fisheries is the interaction of the fish, habitat and the fisher folks. According to Daw et al. [13], climate change will affect fisheries in the context of scale, environment, species, technology, markets, fishers, management arrangement and political contexts. Global warming on account of increasing higher temperature will lead to deep lakes stratification and non-mixing with attendant problems of anoxia at the hypolimnion and fish kills. Ayub [14] observed significant negative correlation between temperature and fish catch in Pakistan lakes. Heavy rainfall and flooding may result in dam collapse with subsequent negative effects on the fisheries of such dam Mustapha [15], while low flow often lead to fish kills (Figure 3). The synergistic effects produced by CC on food webs, stratification, runoff, flow, flooding, and anoxia etc. will affect fish assemblages in the lake or river ecosystems bringing changes in the distribution of pelagic fisheries. Thus, low productivity of the water body, low fish production, less number of adult fishes in the system, abundance of juvenile fish, reduced productivity of commercially important species and a low catch per unit efforts by the fishermen are some of the possible consequences of CC scenarios on artisanal fisheries. Allison et al. [16] has projected reduced fish species diversity in tropical waters. CC could change the state of a lake or bring about regime shifts. For instance, CC could change a eutrophic lake to mesotrophic or oligotrophic one and vice-versa through high run-off, precipitation, evaporation, accelerated eutrophication and other drivers of climate change. This could have devastating effects on the fish production and the entire fisheries of the lake. Thus, fish populations in Africa and Asia could fall as much as 50% with over 20% becoming extinct over the next century if the temperature of the aquatic system continues to warm up to about 5°C above the present trend. Public health problems in the fishing communities could occur due to high precipitation, flooding and runoff all coming from climate change. CC could also make coastal and riverside fishing communities vulnerable to storm surges, tsunamis and sea level rise which might ultimately displace the population. The supply of wild fish seed for stocking in natural or artificial ponds could be threatened as a result of decline in fish production, predation on fingerlings by the adult in the absence of plankton or even diseases outbreak. All these are intrinsically linked to CC. Fish meal and oil which is of commercial importance to artisanal fishermen could be reduced, also on the account of the effects of global warming on fish and its habitat. With the changes in the climate which brings about flooding, high precipitation, drought and other climatic variables, the fishing gears and other associated fisheries processes including preservation, marketing and even fishing periods which hitherto have been adapted to the pre-climatic changes variables would be altered and have to be modified accordingly to suit the new climatic factors in the lake ecosystem for the continued sustenance of the fisheries. This could bring additional burden in terms of cost, technology, reduced profitability, less viability of fishing, etc to the fishermen. Where the fishermen cannot adapt to the new challenges of CC in its fisheries operations, total abandonment of the fisheries may likely occur. The effects of this are better imagined than experienced as it will reduce the diversity of coastal and riverside livelihoods and increase poverty in the fishing communities (Figures 4 and 5).

Figure 3: Effect of annual variations in rainfall in Southern Nigeria over time.

Figure 4: Effect of annual variations in temperature in Northern Nigeria over time.

Figure 5: Effect of annual variations in rainfall in Northern Nigeria over time.

Climate change poses multiple risks to artisanal fisheries both short term such as in increased frequency of events and long term like reduced fish production (Figure 1). The response of particular lake ecosystems to CC will depend strongly on the size, depth and trophic status of the lake. In this context, shallow eutrophic lakes which are common in Africa and highly productive Mustapha [17] will be very susceptible to climate change. Predictions of IPCC [1] also suggested that high intensity of tropical storms with high impacts on fishing communities and infrastructures. This means that developing tropical countries will be more vulnerable because of their lower adaptive capacities. Effective adaptations and mitigation strategies will depend on the prevailing regional conditions associated with human needs in the context of socio-economic necessities and stakeholders pressures on fisheries. Capacity building and resilience through awareness, enlightment and initiatives will be a starting point for adaptive strategies to mitigate the impact of CC on artisanal fisheries. Ecosystem Approaches to Fisheries (EAF), good fisheries governance, management and institutional cooperation could be linked together and used to mitigate the impacts of CC on the ecosystem, production and the fishing communities since the fisheries is aquatic ecosystemcapture based. Other multidisciplinary, multi-stakeholders and holistic approaches to mitigate the impacts could include weather forecasting, disaster preparedness, emergency management, reduction of conflicts associated with CC between fisheries stakeholders, and integration of water and fisheries development programme into national and regional adaptation programmes. Development of sophisticated monitoring programmes in lakes with the use of remote sensing technologies for monitoring the environmental variables, fish and plankton will go a long way in detecting CC and allow for the adaptation and mitigation strategies to be developed in the lake ecosystem. Development of models for climate change impacts on fisheries should be a continuous project in lakes and reservoirs (Figure 6).

Figure 6: Various ways of adaptation and mitigating the impacts of climate change on fish resources.

Green house gas emissions should be slowed down, stored or absorbed through various ways of carbon sinks. Improved energy efficiency performance of all utilities such as in means of transport etc and behavioural changes to reduce GHGs through the adoption of renewable energy, efficient fuel and environmental fiscal measures should be encouraged and advocated.

According to IPCC [1], fishing and fisheries will become impacted if there is a rise in temperature of between 1.5 to 2°C (Figure 7).In order to stem this trend, all contributions to greenhouse gas emissions including gas flaring, use of fossil fuels should be regulated. Understanding climate change and its impacts on the ecosystem will provide accurate decision, capacity building and adaptive management in tackling the problems as it will provide practical, scientific, technical and socio-economic actions to mitigate the challenges currently and in the future. Study of vulnerability of artisanal fisheries to climate change in the likelihood of episodic events of risk exposure, sensitivity and adaptive capacity should be the focus of scientific research in this decade since the complex interactions between climate variables, impacts on fish and fisheries and the socio-ecological responses of the system has not been fully explained. Climate change will produce synergistic and cumulative effects with considerable uncertainty to the extent, magnitude, rate and direction of changes and impacts. Thus, high confidence predictions models of climate change perturbations on fish response in terms of feedbacks, critical thresholds, adaptations, migrations, breeding, and recruitment and so on could be developed to mitigate the impacts and ensure sustainability of artisanal fisheries in Nigeria. According to Barrage and Perry [4], one approach to this is the use of simulation models which involves physical, chemical, biological and ecological models resolutions with their integrations across scales, including the levels of certainty of the projections as well as data to force and validate the models. Establishment of National Adaptation and Mitigation Programme of Action on Climate Change (NAMPACC) in Nigeria which should be fully funded to coordinate researches develop and maintain climate change knowledge, data base, management and learning platform will help minimise the impacts of CC on fisheries.

Figure 7: Impacts of Climate change on fish and artisanal fisheries.