Firth of Lorn is important for undefined aggregations of one shark and one ray species.

Spiny Dogfish (also known as Spurdog) exhibits exceptional residency within Loch Etive, on a spatial scale smaller than anywhere else globally. This area is globally important in this regard as it has the highest known residency of the species (Thorburn et al. 2015, 2025). The aggregation of Spiny Dogfish attracts recreational anglers targeting the species, and scientists who undertake dedicated research trips for the species (using hook-and-line). Between 2010–2020, 255 Spiny Dogfish were caught from various dedicated research surveys in this area. Spiny Dogfish were caught in 2010 (n = 7), 2011 (n = 27), 2014 (n = 114), 2016 (n = 51), and 2020 (n = 56) (Thorburn et al. 2015, 2025; Project SIORC unpubl. data. 2025; Scottish Shark Tagging Programme unpubl. data. 2025). Across the 43 research days in this period, aggregations (determined by three or more individuals being caught from hook-and-line in one trip, lasting a few hours) were reported on 18 days. Aggregations were reported in 2010 (n = 7 days), 2011 (n = 3), 2014 (n = 3), 2016 (n = 3), and 2020 (n = 2). Numbers of animals captured ranged between 3–57 individuals (mean = 16). Furthermore, acoustic data demonstrate year-round residency of Spiny Dogfish in this area, and aggregation behaviour is evidenced by a high number of detections of multiple individuals around different stations within the area, every day (Thorburn et al. 2025). Spiny Dogfish tagged with acoustic transmitters were male (n = 22), measuring 33–75 cm total length (TL), and female (n = 29), measuring 32.0–99.5 cm TL (Thorburn et al. 2025). Spiny Dogfish were detected on each receiver, spanning the entrance of the loch into the deep basin. This is one of the only known locations within the United Kingdom of Great Britain of Northern Ireland with regular and predictable observations of the species year-round. Further information is required to determine the nature and function of these aggregations.

Since monitoring began in 1978, 3,860 Flapper Skates have been recorded in this area. Of these, 2,833 (73.4%) have been recorded since 2010 (Scottish Shark Tagging Programme unpubl. data 2025; Skate Spotter unpubl. data 2025). Higher resolution aggregation data (as indicated by a high number of individuals caught using hook-and-line in a few hours) are available for 1978–2025. Between 1978–2009, aggregations of three or more individuals were recorded in 23 years (n = 223 instances across 828 days of effort). Of these, there were three instances of aggregations of ten or more individuals recorded across three years. Between 2010–2016, aggregations of three or more individuals were recorded in almost every year (n = 113 instances across 247 days of effort). Flapper Skate aggregations were recorded in 2010 (n = 43), 2011 (n = 24), 2012 (n = 10), 2013 (n = 7), 2014 (n = 13), and 2015 (n = 16). Of these, aggregations of ten or more individuals were recorded on four instances across two years. These aggregations are the most regular and predictable across the United Kingdom of Great Britain and Northern Ireland. Firth of Lorn is a critical habitat for Flapper Skate, year-round, given that acoustic detection data demonstrate year-round residency of Flapper Skate across multiple life stages (Neat et al. 2014; Pinto et al. 2016; Lavender et al. 2021). Flapper Skate are observed within the entire depth range of this area (Thorburn et al. 2021). Complementary genetic studies have revealed limited connectivity with other populations (Schwank et al. 2023). Further, there are a number of long-term recaptures, with 248 individuals caught on more than five separate occasions. The most notable case is a Flapper Skate recorded 33 times, demonstrating strong site fidelity or recurring presence in area (Skate Spotter unpubl. data 2025). Since 1978, 2,615 immature Flapper Skate, measuring <160 cm TL, have been recorded through hook-and-line captures (both by recreational anglers and scientists) (Neat et al. 2014; Lavender et al. 2021; Scottish Shark Tagging Programme unpubl. data 2025; Skate Spotter unpubl. data 2025). Of these, most (n = 1,801, 67.3%) have been recorded since 2010. Since 1978, aggregations of five or more immature Flapper Skate have been recorded on 294 days, with most (n = 275) recorded since 2010. Further information is needed to understand the nature and function of these aggregations.