Sexual Maturity Stages and Histological Profiling of Mackerel Scad (Decapterus macarellus) collected from Fisheries Management Area 3 (FMA 3)

Sexual maturity stages (SMS) and histological profiling of gonads are never reported in the Philippines and globally. Thus, this study examined the sexual maturity stages (SMS) of mackerel scad, which were collected by observing the morphological characteristics of gonads and assigning them to their designated maturity stages. Also, the study depicted the gonadal histological profile of mackerel scad through microscopic examination, which underwent tissue processing techniques. The fish samples were in Moro Gulf and Celebes Sea, which are situated at approximately 6°38'02.6"N 123 deg * 4' 03.8^ prime prime E and 3 deg * 36 deg * 11.3 deg * N 122°19'04.1"E, respectively. Moro Gulf and the Celebes Sea are key fishing grounds of Fisheries Management Area 3. The results revealed that from September to November 2022, the highest percentage of individuals belonged to Stage 2 (Developing phase), precisely Stage 2b (Recovering) and Stage 2e (Maturing), indicating a prevalence of premature individuals during this period. The reproductive phases of female mackerel scad were determined based on the most advanced stage of oocyte development, ranging from Stage 1 (Immature) to Stage 5 (Regenerating/Resting) Histological analysis showed the presence of various oocyte types, atretic oocytes, and post- ovulatory follicles (POFs) in different stages. Male mackerel scad was classified into five stages based on germinal epithelium characteristics and the presence of spermatozoa. The study found that female mackerel scad exhibited group-synchronous oocyte development, which suggests at least two different populations of oocytes present at any one time, a relatively synchronous population of larger oocytes (defined as a "clutch") and a more heterogeneous population of smaller oocytes from which the clutch is recruited. The former is the oocytes to be spawned during the recent breeding season, while the latter is the oocytes to be spawned in future breeding seasons, indicating that the fish is a batch spawner. Additionally, oogonial and testicular lobular generation was depicted in Figures 9 and 10 to show the prominent features observed in each maturity stage.