Widespread colonisation of Tanzanian catchments by introduced Oreochromis tilapia fishes: the legacy from decades of deliberate introduction

From the 1950s onwards, programmes to promote aquaculture and improve capture fisheries in East Africa have relied heavily on the promise held by introduced species. In Tanzania these introductions have been poorly documented. Here we report the findings of surveys of inland water bodies across Tanzania between 2011 and 2017 that clarify distributions of tilapiine cichlids of the genus Oreochromis. We identified Oreochromis from 123 sampling locations, including 14 taxa restricted to their native range and three species that have established populations beyond their native range. Of these three species, the only exotic species found was blue-spotted tilapia (Oreochromis leucostictus), while Nile tilapia (Oreochromis niloticus) and Singida tilapia (Oreochromis esculentus), which are both naturally found within the country of Tanzania, have been translocated beyond their native range. Using our records, we developed models of suitable habitat for the introduced species based on recent (1960-1990) and projected (2050, 2070) East African climate. These models indicated that presence of suitable habitat for these introduced species will persist and potentially expand across the region. The clarification of distributions provided here can help inform the monitoring and management of biodiversity, and inform policy related to the future role of introduced species in fisheries and aquaculture.

Seafood from a changing Arctic

We review current knowledge about climate change impacts on Arctic seafood production. Large-scale changes in the Arctic marine food web can be expected for the next 40-100 years. Possible future trajectories under climate change for Arctic capture fisheries anticipate the movement of aquatic species into new waters and changed the dynamics of existing species. Negative consequences are expected for some fish stocks but others like the Barents Sea cod (Gadus morhua) may instead increase. Arctic aquaculture that constitutes about 2% of global farming is mainly made up of Norwegian salmon (Salmo salar) farming. The sector will face many challenges in a warmer future and some of these are already a reality impacting negatively on salmon growth. Other more indirect effects from climate change are more uncertain with respect to impacts on the economic conditions of Arctic aquaculture.

Non-farmed fish contribute to greater micronutrient intakes than farmed fish: results from an intra-household survey in rural Bangladesh

OBJECTIVE

Fish is the most important animal-source food (ASF) in Bangladesh, produced from capture fisheries (non-farmed) and aquaculture (farmed) sub-sectors. Large differences in micronutrient content of fish species from these sub-sectors exist. The importance of fish in diets of vulnerable groups compared with other ASF; contribution from non-farmed and farmed species to nutrient intakes; and differences in fish consumption among age, gender, wealth groups and geographic regions were analysed, using quantitative intra-household fish consumption data, focusing on the first 1000 d of life.

DESIGN

Two-stage stratified sample.

SETTING

Nationally representative of rural Bangladesh.

SUBJECTS

Households (n 5503) and individuals (n 24 198).

RESULTS

Fish consumption in poor households was almost half that in wealthiest households; and lower in females than males in all groups, except the wealthiest, and for those aged ≥15 years (P<0·01). In infants of complementary feeding age, 56 % did not consume ASF on the survey day, despite 78 % of mothers knowing this was recommended. Non-farmed fish made a larger contribution to Fe, Zn, Ca, vitamin A and vitamin B12 intakes than farmed fish (P<0·0001).

CONCLUSIONS

Policies and programmes aimed to increase fish consumption as a means to improve nutrition in rural Bangladesh should focus on women and young children, and on the poorest households. Aquaculture plays an important role in increasing availability and affordability of fish; however, non-farmed fish species are better placed to contribute to greater micronutrient intakes. This presents an opportunity for aquaculture to contribute to improved nutrition, utilising diverse production technologies and fish species, including small fish.