Golfo Nuevo is an important area for undefined aggregations of one shark species.

Tope aggregates seasonally during the austral summer and early autumn in the area. In 2011, 2012, 2015, and 2017 scientific surveys captured and tagged Tope using a longline at a depth between 80–110 m. Between 2011–2012, a total of 17 fishing trips were conducted, with at least one fishing day per month. A bottom-set longline measuring between 500–1,200 m, with hooks spaced every 10 m, was deployed for a maximum duration of 120 min (Irigoyen et al. 2015). Captured Tope were sexed, tagged using traditional dart tags, and their sizes were visually estimated. Catch-per-unit-effort (CPUE) was used to calculate the relative abundance as individuals captured hooks^-1 h^-1. A total of 228 Tope were captured (129 females, 98 males, and one undefined) with higher values of CPUE (0.20 captures hooks^-1 h^-1) during summer and early autumn compared to the CPUE ranging from 0.13–0.02 during the rest of the year (Irigoyen et al. 2015).

Additionally, in 2015 (n = 3) and 2017 (n = 1), scientific fishing days were conducted during February and March using an 800 m bottom longline equipped with 110 baited hooks and set for 120 min (Jaureguizar et al. 2018; A Irigoyen unpubl. data 2025). Across these fishing days, a total of 13, 63, and 14 individuals were captured respectively in 2015, while 36 individuals were captured during one fishing day in 2017 (Jaureguizar et al. 2018; A Irigoyen unpubl. data 2025). The individuals measured 90–150 cm total length (TL) (A Irigoyen unpubl. data 2025). These sizes indicate that individuals captured were immature or subadults, as the species reaches maturity at ~120–170 cm TL for males and 130–185 cm TL for females (Ebert et al. 2021). During the same period, three prospective longline deployments were conducted in surrounding areas of the eastern section of Golfo Nuevo, as well as in San José and San Matías Gulf to the north (A Irigoyen unpubl. data 2025). The recorded CPUE values were 92.5% lower than those observed in the area during the high season and even lower than those of the low season, with a CPUE of 0.015 (captures hooks^-1 h^-1) (A Irigoyen unpubl. data 2025).

Further, in 2021 Baited Remote Underwater Video Station (BRUVS) surveys were undertaken with >400 deployments along the coast of the southwest Atlantic between 41–55°S, including several deployments within the area (n = 97) (P Merlo unpubl. data 2025). Despite the low visibility in the area during January, four BRUVS deployments recorded a MaxN (maximum number of individuals of a species observed in a single frame) of two individuals, and one deployment in the area recorded three individuals in the same frame (P Merlo unpubl. data 2025). Based on the maximum value of MaxN and the medium MaxN, Golfo Nuevo had a high relative abundance of Tope compared with the rest of the areas surveyed, suggesting that this area serves as an aggregation site for the species (Irigoyen et al. 2015; Jaureguizar et al. 2018; P Merlo unpubl. data 2025).

Historical data from commercial fisheries during February and April in 2001 reported a total of 319 Tope with full stomachs, including prey items such as Argentine Hake Merluccius hubbsi, Cuskeels Genypterus blacodes and Raneya brasiliensis, and squid Illex argentinus, with 90% of stomachs surveyed containing food (Elias et al. 2004). It is possible that Tope aggregate in this area to feed, but further information is required to confirm the nature and function of these aggregations.