In social fish species such as Aulonocara nyassae, dominance hierarchies may affect resource allocation, growth, and reproduction. This study evaluated the influence of male social status on growth performance, condition, survival, and reproductive performance.
The experiment was conducted at the Laboratório de Aquacultura (Laqua), Universidade Federal de Minas Gerais (UFMG), Brazil. Four males from each social status (dominant, subdominant, and submissive) (9.62 ± 1.50 g)—were individually allocated to 12 aquaria in a Completely Randomized Design (CRD). Each aquarium housed one male and three females (7.52 ± 1.55 g), following a male-to-female ratio of 1:3 (FAO, 2009). All males and females were measured and weighed after 66 days using a digital caliper and balance. Weight and length data were used to calculate growth parameters, including final weight (FW), average weight gain (AWG), specific growth rate (SGR), final mean total length (FTL), mean length gain (MLG), and Fulton condition factor (K). At the end of the trial, after blood collection, all animals were individually euthanized with eugenol (285 mg L⁻¹) to obtain somatic indexes. The viscera were removed and weighed, and the liver, gonads, and visceral fat were separated to calculate the viscerosomatic index (VSI), hepatosomatic index (HSI), gonadosomatic index (GSI), and intraperitoneal fat index (IPFI). Survival was recorded, and spawning was monitored daily. Eggs were collected prior to hatching, and larvae were reared under controlled conditions for 30 days, during which survival, growth, and developmental parameters were assessed. Female survival was lower when paired with subdominant males (P < 0.05). Dominant males showed higher FW, AWG, VSI, and HSI, while females and progeny associated with dominant males exhibited higher FTL, MLG, SGR, K, total cholesterol (TC), FW, AWG, average egg production, hatching rate, mean number of larvae produced, and final larvae weight and length. Submissive males had higher SGR and FTL, and females associated with submissive males exhibited higher GSI, IPFI, HSI, and VSI (P < 0.05). Subdominant and submissive males also showed higher MLG, GSI, and IPFI (P < 0.05), and Fulton condition factor (K) was higher in both dominant and submissive males (P < 0.05). Male social status strongly influences growth, condition, reproduction, and offspring development in A. nyassae. Dominant males enhance female and progeny performance, while subdominant and submissive males show compensatory traits but may reduce female survival. These findings highlight the need to consider social hierarchies in breeding and aquaculture to optimize growth, health, and reproductive success.