Monitoring biodiversity loss in rapidly changing Afrotropical ecosystems: an emerging imperative for governance and research.

Africa is experiencing extensive biodiversity loss due to rapid changes in the environment, where natural resources constitute the main instrument for socioeconomic development and a mainstay source of livelihoods for an increasing population. Lack of data and information deficiency on biodiversity, but also budget constraints and insufficient financial and technical capacity, impede sound policy design and effective implementation of conservation and management measures. The problem is further exacerbated by the lack of harmonized indicators and databases to assess conservation needs and monitor biodiversity losses. We review challenges with biodiversity data (availability, quality, usability and database access) as a key limiting factor that impacts funding and governance. We also evaluate the drivers of both ecosystems change and biodiversity loss as a central piece of knowledge to develop and implement effective policies. While the continent focuses more on the latter, we argue that the two are complementary in shaping restoration and management solutions. We thus underscore the importance of establishing monitoring programmes focusing on biodiversity-ecosystem linkages in order to inform evidence-based decisions in ecosystem conservation and restoration in Africa. This article is part of the theme issue 'Detecting and attributing the causes of biodiversity change: needs, gaps and solutions'.

Wetland fishes avoid a carbon dioxide deterrent deployed in the field.

Biological invasions are poorly controlled and contribute to the loss of ecosystem services and function. Altered watershed connectivity contributes to aquatic invasions, but such hydrologic connections have become important for human transport. Carbon dioxide (CO2) deterrents have been proposed to control the range expansion of invasive fishes, particularly through altered hydrologic connections, without impeding human transport. However, the effectiveness of CO2 deterrents needs to be further evaluated in the field, where fishes are situated in their natural environment and logistical challenges are present. We deployed a proof-of-concept CO2 deterrent within a trap-and-sort fishway in Cootes Paradise, Ontario, Canada, to determine the avoidance responses of fishes attempting to disperse into a wetland. We aimed to describe deterrent efficiency for our target species, common carp, and for native fishes dispersing into the wetland. Our inexpensive inline CO2 deterrent was deployed quickly and rapidly produced a CO2 plume of 60 mg/l. Over 2000 fishes, representing 13 species, were captured between 23 May and 8 July 2019. A generalized linear model determined that the catch rates of our target species, common carp (n = 1662), decreased significantly during deterrent activation, with catch rates falling from 2.56 to 0.26 individuals per hour. Aggregated catch rates for low-abundance species (n < 150 individuals per species) also decreased, while catch rates for non-target brown bullhead (n = 294) increased. Species did not express a phylogenetic signal in avoidance responses. These results indicate that CO2 deterrents produce a robust common carp avoidance response in the field. This pilot study deployed an inexpensive and rapidly operating deterrent, but to be a reliable management tool, permanent deterrents would need to produce a more concentrated CO2 plume with greater infrastructural support.

A habitat-based framework to predict the effects of agricultural drain maintenance on imperiled fishes.

One third of the total global land viable for agricultural production has artificial drainage systems. These drainage systems can provide important habitat for fishes and, in some cases, imperiled fish species vulnerable to impact by drainage maintenance activities. A framework to provide quantitative assessments of the effects of maintenance activities on imperiled fish species is needed. In this study, a six-step habitat-based framework was developed to predict suitable habitat for two at-risk species in an agricultural drain: the Endangered Pugnose Shiner (Notropis anogenus) and the Special Concern Blackstripe Topminnow (Fundulus notatus). Using the framework, spatial models were developed to assess the effects of proposed drain maintenance on the overall amount of suitable habitat, habitat patch size, and connectivity of habitat patches. Maintenance had a significant impact on habitat connectivity, but did not significantly reduce the habitat size of isolated patches. The amount of suitable habitat available after maintenance fell below the minimum area for population viability (MAPV) for the Pugnose Shiner, but not the Blackstripe Topminnow. Future impact assessments of drain maintenance should incorporate population viability analysis, coupled with habitat patch analysis (patch size and connectivity), to quantitatively test consequences of proposed alteration to the viability of spatially structured populations.

Macrohabitat associations of fishes in shallow waters of the Detroit River.

Seasonal variation in large-scale habitat selection by fishes in shallow, Canadian waters of the Detroit River was examined. Fish communities were compared among three river segments (upstream, middle and downstream) consisting of areas of shallow water habitat separated by wide hydrologic barriers of deep, flowing water and between inshore and offshore areas. In spring, the most unique, diverse and abundant fish assemblages were found at inshore sites in the middle segment where the largest remaining wetland habitats are located. Fishes used inshore habitat to spawn and probably avoided offshore areas because macrophyte cover was not available in spring. In summer, juvenile gizzard shad Dorosoma cepedianum and white bass Morone chrysops were observed in high densities in the upstream segment, probably migrating downstream from Lake St Clair. There was little difference in the fish assemblage among macrohabitats in autumn. The upstream segment appeared to be the most degraded, because it contained no species that were not found in the other segments, had a paucity of uncommon species and had significantly more non-native species. This state was attributed to the infilling of coastal wetlands by urban land use and a resulting loss of habitat heterogeneity. The middle segment, with the only remaining wetland habitats, had the greatest occurrence of uncommon species and the only species at risk found in this study. Conservation and restoration efforts should be greatest for wetlands; however, shallow offshore areas provide important fish habitat in summer and autumn.