Study Area The data were collected by researchers from Operation Wallacea in Honduras, a country with coastlines along both the Caribbean Sea and the Pacific Ocean. The research sites are located along the northern coast of Honduras, across the bay of Tela, and categorised into the two reef systems: Banco Capiro and La Ensenada. Within each of these areas, multiple dive sites were surveyed (see Table 1). Banco Capiro is situated approximately 8km from the shore in the centre of the bay, while La Ensenada is towards the East of the bay, approximately 0.4km from the shoreline (see Figure 1). Sampling and Survey Design Sampling spanned June to August across the years 2014 to 2024. The study included a total of 2,373 lionfish, all of which were culled during surveys, identified as P. volitans through subsequent dissections, and collected from eleven dive sites within Banco Capiro and La Ensenada. A total of 327 unique lionfish aggregations were recorded during the surveys included in this study. This study follows a repeated seasonal survey design, with lionfish observations collected annually during a consistent sampling window (June–August) across the two reef systems. Surveys were conducted using comparable methods across years, with a single SCUBA diver conducting the lionfish extractions on each dive to provide a consistent effort, enabling interannual comparison of population dynamics. Roving diver surveys were conducted, with lionfish culled using a Hawaiian sling pole spear and transferred to a Zookeeper container (Searle et al. 2012; Lionfish Hunting 2017). For the purposes of this study, an aggregation was defined as the occurrence of two or more lionfish observed within 1 m proximity of another lionfish, with both being non-moving, indicating local clustering within a survey unit rather than general co-occurrence on the reef. While lionfish are known to aggregate on coral reefs, this study focuses on temporal variation in aggregation size and structure across sites and sampling periods. Interannual comparisons confirm consistency in survey timing (June–August), sampling approach, and site coverage across years, allowing relative differences in lionfish abundance and aggregation patterns to be assessed over time. On return, lionfish were dissected immediately or refrigerated and dissected within 12 hours. Dissections followed Green et al. (2012). Sex was determined visually from gonad morphology using the lionfish sex determination and gonad staging key, based on gonad size, presence of gonadal masses, length:width ratio, and colour.