Mahmoud 1985

Methods	Study design: controlled time series Study location: Gezira irrigated area, Sudan Study dates: January to December, but the two years were not specified Transmission intensity: not specified Malaria parasite species: not specified Primary vectors: An. arabiensis Breeding sites: small temporary pools Baseline data: none
Participants	Not applicable
Interventions	Fish species: G. holbrooki (Note: This study refers to G. affinis holbrooki, as these fish were then considered a subspecies of G. affinis. This subspecies is now recognized as a full species) Indigenous fish species used: no Fish source: rearing ponds at Wad Medani, 20 to 25 km from trial sites Populated sites: 20 irrigation canals, 1 m in depth, 2 m in width, and 4 to 10 km in length; five control canals Restocked: yes Co-intervention: none
Outcomes	Average larval density of An. arabiensis/100 dips, according to instar stage Methods: larval dipping at two sites per km in each canal, 10 dips per site
Source of funding	Malaria Control Project, Ministry of Health, Sudan
Notes	Flow of water from large branch canals was controlled by gates opened at certain times; this system deprived the Gambusia of free movement into the smaller canals, which usually are richer in mosquito larvae than the larger ones, where the fish had originally been stocked
Risk of bias
Bias	Authors' judgement	Support for judgement
Study design	High risk	Controlled time series study
Site selection	Unclear risk	"Medium size irrigation canals of about 1 m depth, 2 m width, and 4-10 km length, officially classified as minor canals, were selected as sites for the trials. Twenty such canals were seeded with Gambusia...while five others were used as control"
Site allocation	Unclear risk	Unclear how treatment for each site was chosen for ponds
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Unclear whether assessors were blinded to treatment
Baseline values	Unclear risk	Not reported. Fish release in October and measurements not taken until following January
Number of sites	High risk	May be inadequate, as only five sites in the control group