Bringing Back the Burbot (Lota lota L.): Assessing Instream and Floodplain Habitat Availability to Support the Reintroduction of a Nationally Extinct Fish

Species reintroductions can play a major role in addressing biodiversity declines. Fish species reintroductions are, however, complex and require the investigation of multiple factors: physical habitat, water chemistry and hydrology, among others. The burbot (Lota lota, L.), the only freshwater member of the Cod family (Gadidae), was extirpated from English rivers due to habitat modification, leading to a loss of suitable spawning and larval nursery habitat. This paper uses a bespoke field survey, grounded in burbot ecology, to assess instream habitat availability for a proposed English burbot reintroduction site, the River Wissey, eastern England. Using an ex situ assessment, the study compares the Wissey in terms of floodplain spawning and larval nursery habitats with three Belgian sites where a burbot reintroduction is on-going. The study found that the English candidate reintroduction site had 10% of the main channel habitat available for instream spawning, with 15% available for juveniles, 20% for adults and 42% classified as unsuitable for any life stage. The floodplain habitat analysis determined that the English reintroduction site had a potential floodplain spawning habitat capacity of 56%, compared to < 42% at the Belgian comparison sites. Overall, habitat associated with each burbot life stage is present at the English candidate reintroduction site. Based solely on physical river habitat, this paper recommends river restoration before the reintroduction is attempted to increase connectivity between extant good-quality habitat patches and between the main channel and floodplain. To achieve a successful burbot reintroduction, it is concluded that more research is needed on hydrological and thermal dynamics, as well as food–web interactions.