Evaluation of growth, sex (male proportion; sexual dimorphism), and color segregation in four cross combinations of different strains of XX female and YY male Nile Tilapia

Four cross combinations of different YY male and female Nile TilapiaOreochromis niloticusstrains were evaluated for growth, sex, and color segregation. Red color parental strains included blotched phenotypes. The Genetically Improved Farmed Tilapia (GIFT) was the only dark (wild-type) color parental strain. Fish of the same age and cross were stocked in three replicate tanks for four crosses in one recirculating system for 167 days. Data recorded included feed consumed, body weight, total length, color, sex, and fillet weight. YY males crossed with GIFT females (Cross 2) exhibited superior growth that was significantly different (p <.05) to other three crosses. Male proportions were 79-100%. Only YY males crossed with the LSA female strain (Cross 4) yielded 100% males, but, Cross 4's productivity was inferior to that of Cross 2. Body weight advantage of males over females was 28.7-84.2%. Color segregation indicated that red color trait in Nile Tilapia is autosomal dominant, and black patch coverage was variable. This study showed that different parental strain combinations clearly impact productivity traits, and that YY male technology combined with crossbreeding provide the opportunity for genetic improvement and development of commercially beneficial superior traits in Nile Tilapia.