Ría Deseado is an important area for undefined aggregations of one shark species.

There are historical records of fishing tournaments targeting Broadnose Sevengill Sharks in the area. Since the 1970’s fishing competitions have reported captures of young-of-the-year (YOY) and juvenile Broadnose Sevengill Sharks in this area (Cedrola et al. 2009; C Pantano & AJ Irigoyen unpubl. data 2025). In 2003–2004, interviews were conducted with recreational fishers (n = 15) in the area to gather information on the best fishing locations and seasons for Broadnose Sevengill Sharks (Caille & Cedrola 2007). Historical local ecological knowledge from fishers reported that the fishing season extends from November to February and that the best areas for fishing, due to the abundance of individuals, are located within the area, particularly inside the Ría, providing support for species aggregations in the area. They also noted that the majority of captured individuals are juvenile females (Caille & Cedrola 2007), suggesting there could be a reproductive purpose for this aggregation. A survey of the fishing tournaments and recreational fishery between 2004–2007 collected sex, size (total length; TL), and weight of sharks caught in the area (n = 63; Cedrola et al. 2009). Broadnose Sevengill Sharks caught in the area measured between 115–232 cm TL, with a mean of 178.1 cm TL. Demographically, juvenile females dominated the catches (Cedrola et al. 2009).

In January–February 2025, a combination of sports fishers and scientific fishing efforts using longlines caught and measured Broadnose Sevengill Sharks in the area (n = 44; 125–250 cm TL). During a four-hour shore fishing session, 15 sharks were caught demonstrating the aggregative nature of the species in the area (C Pantano & AJ Irigoyen pers. obs. 2025). Size-at-maturity for this species is ~150–180 cm TL (Ebert et al. 2021), indicating some of the individuals were immature. Most captures were of females (93.2%; n = 41) and captures were concentrated at La Ventana and El Puesto in the area.

Ría Deseado is potentially important for reproductive or feeding aggregations of this species. Regionally, the area has been proposed as a secondary nursery area for larger juvenile Broadnose Sevengill Sharks (De Wysiecki et al. 2023). Aggregations of smaller individuals have been confirmed in northern Argentina, where it is presumed the warmer waters provide primary nursery habitat for the growth of younger life stages of this species. Whereas it is proposed the colder conditions of coastal aggregation areas further south may provide better feeding opportunities for larger juveniles (Irigoyen et al. 2019; De Wysiecki et al. 2023).  Broadnose Sevengill Sharks are known to seasonally aggregate in other parts of the globe for feeding or reproductive purposes (Ebert 1989; Lucifora et al. 2005; Barnett et al. 2010; Abrantes & Barnett 2011; Williams et al. 2012; Stehfest et al. 2014; Hammerschlag et al. 2019). However more information is needed to determine the nature and function of this aggregation.