The context setting in the report assumes significant worry for the global community on the assessment that the current ongoing decline in migratory freshwater fishes is leading to millions of people worldwide losing their cultural, spiritual, health, ecological and economic benefits.
By Salam Rajesh
Almost one in three of all freshwater fish species and 25 percent of the freshwater fish species globally are threatened with extinction (IUCN 2023), and migratory fishes are disproportionately threatened compared to non-migratory fishes.
This seemingly hard-hitting analysis comes with suggestions for remedial measures in future times as is critically examined in the World Fish Migration Foundation-The Netherlands’s latest technical report, ‘The Living Planet Index (LPI) for Migratory Freshwater Fish 2024’ (Deinet, S. et al, 2024).
The context setting in the report assumes significant worry for the global community on the assessment that the current ongoing decline in migratory freshwater fishes is leading to millions of people worldwide losing their cultural, spiritual, health, ecological and economic benefits. Migratory fishes that spend all or parts of their life cycle in freshwater are highly threatened, the report stated.
The other important aspect featured in the report is the urge for the protection and restoration of free-flowing rivers and swimways for migratory fishes considering the relative importance of river connectivity for migratory fish and the multiple benefits they provide to ecosystems and society in general.
While urging for the inclusion of freshwater migratory species and swimways in the National Biodiversity Strategic Action Plans (NBSAPs) and delivery of inland waters-related commitments as outlined in the Kunming-Montreal Global Biodiversity Framework (KMGBF), the report stressed the need to develop international, national and sub-national river basin planning and strategies to identify critical swimways and avoid development ‘that would block or otherwise degrade them’.
The report is critical in emphasizing the need to restore the environmental flow regimes and river connectivity by targeted removal of barriers, in specific dams, barrages, weirs, and other such man-made structures obstructing the free-flow of the rivers and largely disrupting the movement of the migratory fishes.
In cases where physical removal of the man-made structures is not possible immediately, the report suggests adding effective fishways to existing barriers, such as fish ladders or by-pass channels, in locations where removal is not feasible or possible as the case may be. The report further urged for reducing pollution in freshwater ecosystems and their impact on the species dependent on them.
On addressing existing threats to freshwater fishes, the report urges to investigate the relationship between the life-history traits and the external threats associated with the greatest declines in migratory freshwater fish species.
This suggestion is quite specific and relevant to migratory fish species population decline in Manipur’s floodplains as a result of obstruction by a man-made structure – the contentious Ithai Barrage – for the 105 megawatt capacity Loktak Hydroelectric Power Project which is a major nemesis for inducing biodiversity loss and species decline in the State.
The suggestion for design measures for the protection and the restoration of migration routes that sustain ecologically, culturally and economically important fish species, in line with international policy such as the Kunming-Montreal Global Biodiversity Framework, is certainly relevant to Manipur’s floodplains where wetlands that once were trimming with abundant migratory fish population coming upstream from the Chindwin-Irrawaddy river system in Myanmar flourished and provided means of food, livelihood and economies for the local people who are primarily fish-consuming population.
The physical hindrance to the traditional passage of the migratory fish species along the Manipur River swimway is primarily cited as reason for inducing sharp decline in indigenous fish species in wetlands within the Manipur River Basin, incurring heavy losses for local communities who eke their living from the fish resources through capture fishery.
The structural design for the 5-sluice gates operating Ithai Barrage does not contain provision for fish ladder or by-pass channel to re-direct the traditional passage of important migratory fish species like Cirrhinus reba, Osteobrama belangeri, Labeo bata and Wallago attu that are of food value and having social, cultural and religious value particularly for the Meitei population settled in the Manipur floodplains.
The decline in the traditional fish population had impacted the economies of the local fishing community tremendously. Loktak freshwater lake that once produced around 60 percent of the total fish produce in Manipur State now has to be replenished with imported Indian Major Carps (IMCs) to provide earning and livelihood for the local people.
State fishery department under the Government of Manipur is presently working to ranching around 20 lakh fingerlings in select rivers across the State to replenish the declining fish population. Critics, however, are skeptical of the department’s decision to introduce IMCs in traditional waters in view of possible damages to the river ecology in future times and of the possibility of introduced species dominating over the native species.
This aspect is specifically stressed in the report which urges for highlighting the positive economic outcomes of river protection and restoration, including the economic benefits that migratory freshwater fish provide to societies locally and globally.
Analyzing threats, the report states that the most reported threat was habitat degradation and change (35%), which together with habitat loss accounted for 50% of all reported cases. The second most reported threat was overexploitation, which accounted for near one-third of the recorded threats.
At the regional level, habitat-related threats were the largest threat category in almost all regions, adding to more than 50% of all the threats in Africa, Asia and Europe. Overexploitation was widely cited as a threat in all regions, especially in Africa, Asia, and Latin America and Caribbean, the report stated.
Considering the observed and perceived threats, the report suggests that management interventions may mitigate the effects of identified threats on species population trends. For migratory freshwater fish species, these interventions can take a variety of different forms, for example, the management of fisheries, habitat restoration, dam removal, setting up conservation areas, species-focused management and legal protection can largely address the threats.
The report, however, observed that in contradiction to suggested measures, habitat management accounted for only 9 percent of the recorded management activities, despite the prominence of habitat-related threats to populations in the data set. At the local context, this observation is quite true of in Manipur’s case where there is less of focus on habitat restoration and management as of date.
The report’s findings indicated that populations of the migratory freshwater fishes have been declining steadily since 1970 throughout their global distribution. The assessment is authenticated using up-to-date migratory coding of the IUCN Red List compared to the GROMS coding in previous analyses (Deinet et al., 2020). Average declines are apparent in tropical and temperate zones, in all regions and even in those populations that are managed, the report further stated.
The report expressed deep concern that given plans to vastly expand hydropower in Asia (particularly in the Ganges-Brahmaputra, Indus, Irrawaddy, Salween and Mekong Basins), it is anticipated that habitat will be further degraded and lost, and that declines in migratory fishes will accelerate in the region in the coming decades.