Studies of fish reproductive biology often involve quantitative estimates based on histological sections of the ovaries. Prior characterization of gonad oocyte distribution patterns in females is fundamental to these studies. Heterogeneous distribution requires a standardized sampling protocol to prevent bias in data such as fecundity estimations. In contrast, homogeneous distribution allows sampling of any portion of the gonads with no risk of bias. A preliminary study was done of gonad oocyte distribution mode in a hogfish Lachnolaimus maximus population in the southern Gulf of Mexico. A total of 23 sexually-active females were selected and classified by reproductive stage. Six histological sections were taken from the anterior, middle and posterior regions of the left and right ovary lobes of each individual. Digital image processing (AxioVision and Image ProPlus programs) was used to estimate oocyte density per unit area in different development stages. Contingency tables were used to analyze oocyte distribution frequencies between the regions of each lobe and between the lobes of each ovary. This was supported with a Pearson’s χ² test for goodness-of-fit and a replicated G test to confirm distribution heterogeneity. Oocyte type distribution was homogeneous in almost all the females regardless of ovary region or lobe. This was particularly the case for females in the actively spawning reproductive subphase. Females in this subphase are normally used to estimate batch fecundity in fish species such as L. maximus, which have asynchronous oocyte development and batch spawning. However, heterogeneity was present in tertiary vitellogenesis oocytes in the right lobe of females in the spawning capable reproductive phase. In these cases, it is preferable to take histological sections from any region of the left ovary lobe to ensure unbiased estimation of fecundity and adequate characterization of this species’ sexual cycle.

Snappers exhibit reproductive trait plasticity in response to habitat distribution. Lutjanus griseus is among the most economically important snappers in the western Central Atlantic but has received limited study in the region. Data on the reproductive biology of the L. griseus population were collected on the continental shelf of the Yucatan Peninsula, Mexico. Over a nineteen-month period, 1236 specimens were captured monthly in three Yucatan artisanal fishing fleet operational areas. Data were grouped by month to generate an annual analysis. Individual sex and maturation status were identified by gonad histology. Median size did not differ between females (33.2 cm fork length [FL]) and males (33.3 cm FL), and the sex ratio was balanced (F:M=0.98:1.00). Size at maturity was 24.2 cm FL for females (38% of maximum size reported for the species) and 22.8 cm FL for males (36% of maximum size), and the spawning season ran from May to September. The results confirm that this population exhibits the typical reproductive pattern of snappers distributed on continental shelves or in shallow water areas and provide critical data for stock assessment and implementation of management measures for L. griseus stock in the southern Gulf of Mexico.

Overexploitation is the main anthropogenic threat to groupers (Epinephelidae) that aggregate to spawn. Fishing negatively affects their reproductive success and indirectly harms fishery economic yield. In the southern Gulf of Mexico, grouper catches, which include thirteen species, are in decline. A lack of biological information on each exploited species prevents optimising fishery management. Using histological examination of the gonads, the reproductive traits of red hind Epinephelus guttatus and yellowfin grouper Mycteroperca venenosa were studied from January 2008 to October 2009. Collections were made at two reef systems (Alacranes Reef and Bajos del Norte) on the continental shelf of the Yucatan Peninsula, Mexico, where these species form transient spawning aggregations. The results confirmed that previously identified spawning aggregation sites at both reefs constitute productive seasonal and perennial “hotspots” for both groupers; they spawn annually between January and April. Females of these protogynous hermaphroditic species exhibit a reproductive strategy characterised by asynchronous ovarian development organisation and ovulation. Sex ratios and maximum sizes at each reef suggest that populations of both groupers had a good conservation status as of the late 2000s. Both reefs are now marine protected areas, and a discussion is made of the consequent possible benefits to grouper population conservation and sustainability in the southern Gulf of Mexico.