Magdalena & Almeja’s Bay is an important reproductive area for one shark and one ray species.

Young-of-the-year (YOY) and juvenile Bull Sharks are regularly observed in this area (Pelagios Kakunjá unpubl. data 2026). Historical research identified the area as a nursery area for Bull Sharks in 1998–1999 based on traditional ecological knowledge from fishers and records of neonate Bull Sharks (n = 3). Animals ranged in size between 72–87 cm total length (TL) and were reported from artisanal fishery landings sampled in summer months (Bizzarro 2005). The size-at-birth for the species is 56–81 cm TL (Ebert et al. 2021) and individuals <99 cm TL are typically classified as YOY in the western Pacific (Pillans et al. 2020). Fishers indicated that pregnant females entered these bays from March through May and pup in the late spring and early summer months before departing (Bizzarro 2005). Between 2023–2026, small Bull Sharks were recorded and photographs posted online from this area. They were captured in artisanal fishing nets in shallow and protected parts of the area linked to channels and mangrove systems. At least 12 YOY Bull Sharks, with visually estimated sizes of <90 cm TL were observed in the lagoon during the months of October–March during this period. Due to the implementation of a seasonal fishing ban for shark and rays in the area during the summer months (May–July), neonates and YOY are likely underreported during this period. Additionally, between 2025–2026, two interviews were conducted with local artisanal fishers operating within the area, each with more than 25 years of experience and representing multi-generational knowledge (Pelagios Kakunjá unpubl. data 2026). Fishers indicated that although sharks are not the primary target species for some fisheries, small Bull Sharks are regularly incidentally captured in nets or observed during routine fishing activities. Low numbers likely reflect limited survey effort and the absence of formal monitoring in the area. The area represents the only suitable habitat for neonate and YOY Bull Sharks along the southern coast of the Baja California Peninsula, comprising shallow lagoons with extensive mangrove coverage and pronounced estuarine gradients (Zaitsev et al. 2010). Contemporary records indicate that Magdalena Bay continues to be used by small Bull Sharks in a regular and predictable manner.

Shovelnose Guitarfish use the area seasonally as a pupping and mating ground based on historical data (1990–2002), while contemporary data (2011–2014) shows the seasonal prevalence of the species in the area (Villavicencio-Garayzar 1993; Downton-Hoffmann 2007; CONAPESCA 2014; Medina-Trujillo 2021). Between 1990–1991, six surveys were conducted at the artisanal landing site of Puerto Viejo within the area during August, October, and December (1990), and March and June–August (1991). Fishing was carried out using gillnets with mesh sizes ranging from 10 to 30 cm (Villavicencio-Garayzar 1993). A total of 429 Shovelnose Guitarfish were captured, the majority (n = 419) between June and August (Villavicencio-Garayzar 1993). Of these, 96 females were measured, ranging from 83–137 cm TL, and pregnancy was confirmed in 32 individuals during June. Males ranged from 74–98 cm TL (Villavicencio-Garayzar 1993). The reported size-at-birth in the area ranges from 20 to 24 cm TL (Downton-Hoffmann 2007). Size-at-maturity is 57–99 cm TL for females and 63–110 cm TL for males (Villavicencio-Garayzar 1993; Downton-Hoffmann 2007). The adult sex ratio in June was strongly female-biased (53:1) while, by July, with the arrival of mature males carrying sperm, the ratio shifted to 1.66 females per male (Villavicencio-Garayzar 1993). Histological analyses, combined with seasonal patterns of abundance in the area and traditional ecological knowledge from fishers, indicate that the Shovelnose Guitarfish gives birth during July–August, followed almost immediately by ovulation and mating. After reproduction, females leave the bay carrying fertilised eggs. Embryonic development appears to slow or temporarily arrest from mid-August through April, resuming in April–May when females return to the area to complete gestation (Villavicencio-Garayzar 1993). By early June, embryos were either absent or measured only 1.5–4.0 cm TL, and females sampled in October and December contained eggs but no visible embryos (Villavicencio-Garayzar 1993). Additional sampling conducted in 1992, 1993, 1998, and 2002 at the same landing site recorded 916 females (40–142 cm TL) and 320 males (40–112 cm TL), with surveys carried out throughout the year (Downton-Hoffmann 2007). Peak abundance (89.1%) occurred between May and August. Only adult females were recorded in June (>400 individuals), while adult males appeared from late July to early August. Pregnant females were recorded in June–July 1992 (n = 66 pregnant females carrying 340 embryos), 1993 (n= 36), 2002 (n = 243 carrying 225 embryos), and 2004 (n = 25 carrying 180 embryos; Downton-Hoffmann 2007). Due to the lack of dedicated contemporary surveys, as well as the implementation of a fishing ban (May–July, in place since 2012) that coincides with the period of highest abundance, recent data for this species in the area are limited. However, landings of the species were recorded through 2014, highlighting the regular and continuous use of this area as a reproductive habitat along the western coast of the Baja California Peninsula (Villavicencio-Garayzar 1993; Downton-Hoffmann 2007; CONAPESCA 2014; Medina-Trujillo 2021).