GONAD PROXIMATE AND FATTY ACID COMPOSITION, AND STAGES OF GONADAL DEVELOPMENT OF WILD KING ANGELFISH Holacanthus passer
The King Angelfish, Holacanthus passer, is geographically distributed from the northern Gulf of California, Mexico, to Peru in South America. Its eye-catching colors, both as a juvenile and as an adult, make it a valued species in the ornamental marine fish market. However, the availability of King Angelfish in the aquarium trade is solely based on the capture of wild individuals, since it has never been bred in captivity. Conservation regulation protects this species in Mexico, although there are reports of illegal catch and trade. Controlled, captive breeding of King Angelfish would contribute to satisfy the demand for this species, as well as to lessen fishing pressure on wild populations and even serve stock enhancement purposes. To achieve this, knowledge of the stages of gonad development and gonad chemical composition is essential to determine basic aspects, such as size or age at first maturity and length of the reproduction season, among others, which are relevant for ornamental aquaculture management. The objective of the present study was to investigate the gonad fatty acid profile and proximate composition, and stages of gonadal development of wild H. passer from the Gulf of California.
After a scientific collection permit was issued, forty five fish were captured with hand nets between July and August 2014 in the surroundings of "El Datil" (Latitude: 28°42ʹ53.08"N; Longitude: 112°17ʹ12.20"W), Gulf of California, Mexico. Fish were individually measured and weighed to calculate the Fulton´s condition factor (K) = (wet body weight, g/total length (TL)3, cm) × 100. Gonads were removed to calculate the gonadosomatic index (GSI) = (gonad weight, g/wet body weight, g) × 100. Subsequently, gonads were used to analyze their fatty acid profile by means of gas chromatography and their proximate composition following standardized, chemical methods. In addition, histological methods were applied, including fixation, paraffin wax embedding, sectioning, and hematoxylin-eosin staining in order to identify the stages of gonadal development.
Females had notably smaller size, but greater GSI value than males, while the Fulton´s condition factor was 3.11 and 2.80 for females and males, respectively (Table 1). Analysis of the gonad proximate composition revealed that females had more crude protein (18.09%), but less crude lipid (5.17%) content than males (13.49 and 11.35%, respectively). Poly and highly unsaturated fatty acids (PUFA + HUFA) were the main constituent fatty acids in gonads of both sexes (♀: 31.1 and ♂: 22.6 mg PUFA+HUFA/g of wet tissue). Docosahexaenoic acid (DHA) had the greatest relative abundance among individual fatty acids in this tissue (♀: 14.4 and ♂: 11.6 mg DHA/g wet tissue).
The evaluation of the stages of ovarian and testicular development indicated the presence of mature and spent males and females at this time of the year.