Firth of Thames and Inner Hauraki Gulf is an important reproductive area for four shark species.

A pregnant White Shark measuring 550 cm total length (TL) and containing five near-term embryos (~150 cm TL) was caught off Gannet Rock in 2003 representing one of the few observations of pregnant White Sharks with embryos worldwide (Beston 2003). Between 1919–2022, 47 White Sharks were documented from the area with 37 (78.7%) recorded since 2000 (CAJD unpubl. data 2024; iNaturalist 2024a). Most records are from Tamaki Strait, Rangitoto Channel, Whangaparaoa Peninsula, and Kawau Bay (CAJD unpubl. data 2024). Observed lengths of 45 free-living White Sharks from the area ranged from 160–550 cm TL, with an average of 314 cm TL. Of these, 21 (47%) were <250 cm TL, two measured 180 cm TL, and one 160 cm TL (CAJD unpubl. data 2024). Estimated size-at-birth for the species in the area is ~152 cm TL while for YOY it is ~180 cm TL (Finucci & Ó Maolagáin 2022), confirming that individuals observed were YOY and small juveniles.

Aggregations of gravid female Tope have been reported in the area between Te Kouma Harbour and Deadman’s Point, in Inner Channel off Mahurangi Peninsula, and off northeast Kawau Island from catches by commercial fishers and recreational anglers since the 1990s. Further, YOY have been reported throughout the Firth of Thames and Tamaki Strait (Hurst et al. 2000; Morrison et al. 2002, 2003; D Kellian pers. comm. 2014). Reports since 2017 have shown the regular presence of neonates and YOY based on their size (<60 cm TL; iNaturalist 2024b; CAJ Duffy pers. obs. 2024). Size-at-birth in the area is ~30–35 cm TL while YOY measure <50 cm TL (Francis & Mulligan 1998).

Female Rig enter shallow inlets and estuaries to pup in spring and summer with neonates found in Tamaki Estuary and Waitemata Harbour, but pupping likely occurs in other sheltered inlets and estuaries in the area (Francis et al. 2012; Getzlaff 2012; Aguirre et al. 2016). Between February–March 2011, set net surveys were conducted in 14 major harbours and estuaries throughout New Zealand (Francis et al 2012). Sixty-five of the 120 Rig sampled in the area were neonates or YOY individuals according to their size (<45 cm TL; Francis & Francis 1992; Francis et al. 2012). All individuals were caught at <6 m depth (Francis et al. 2012). Waitemata Harbour and Tamaki Estuary were reported as high-value nursery habitats for Rig based on the high number of neonates and YOY recorded compared to other areas in New Zealand (Francis et al. 2012). Neonates and YOY Rig have been reported as abundant in the area in spring and summer since the 1980s (Francis et al. 2012) and between 2000–2001 (Hendry 2004). Recent observations between 2016–2024 confirm the regular and contemporary presence of these life stages (CAJ Duffy pers. obs. 2024; iNaturalist 2024c).

Commercial catch data (set nets, bottom longlines, and bottom trawls) from 2005–2014 and from trawl surveys conducted between 1961–2014 showed that neonate and YOY Smooth Hammerheads are regularly caught in the Firth of Thames and Inner Hauraki Gulf (Francis 2016). Of 208 individuals recorded in trawl surveys, 55.3% (n = 115) were <60 cm TL, with smaller sharks observed from January–March (Francis 2016). The reported size-at-birth for the species is 49–63 cm TL, and juveniles probably grow about 25 cm per year during the first four to five years of life, confirming these are either neonates or YOY (Ebert et al. 2021; Coelho et al. 2011). Three specimens found discarded on sandflats at Firth of Thames in February 2003 ranged from 56-61.5 cm TL (CAJ Duffy unpubl. data 2024). In addition, juveniles are sometimes observed in large aggregations in the area (CAJ Duffy pers. obs. 2024). Estuarine areas in the Firth of Thames provide a large abundance of prey (e.g., Anchovy Engraulis australis) for these early life stages to feed on. These life stages are still observed in the area by recreational anglers (CAJ Duffy pers. obs. 2024).