two tributaries, the Wairoa River to the west from modern-day Clevedon and the Umangawha Stream to the east, at Colville, Coromandel Peninsula. This river flowed north, along the plains, turning east and exiting towards the Pacific Ocean along the modern-day Colville Channel between the Coromandel Peninsula and Great Barrier Island. Islands In the west of the gulf lie a string of islands guarding the mouth of the Waitematā Harbour, one of Auckland's two harbours. These include Ponui Island, Waiheke Island, Tiritiri Matangi and the iconic dome of Rangitoto Island (a dormant volcano), which is connected to the much older Motutapu Island by a causeway. The islands are separated from the mainland by the Tamaki Strait and Rangitoto Channel. Other islands in the gulf include Browns Island, Motuihe Island, Pakihi Island, Pakatoa Island, Rakino Island, and Rotoroa Island in the inner gulf, around Waiheke and Rangitoto; Tarahiki Island just east of Waiheke; Motukawao Islands and Whanganui Island in the lee of the Coromandel Peninsula; and Channel Island in the outer gulf. In March 2020, a small excavation was carried out in a large coastal midden on Otata Island. In January 2018, huge swells in the Hauraki Gulf caused widespread damage to its coastal areas and in only a few hours, the coastline or Otata had been reduced by up to 5 meters, exposing the midden. The aim of the excavation was to record this information before it is lost to erosion and was carried out in partnership with Ngāi Tai ki Tāmaki, the landowners. An understanding the changing marine environment around the island will also form part of the work. Firth of Thames At the southern end of the gulf is the wide, relatively shallow Firth of Thames. Beyond this lie the Hauraki Plains, drained by the Waihou River and the Piako River. The Hunua Ranges and hills of the Coromandel Peninsula rise on either side of the Firth. Ecology Species Some particular common or known animals include bottlenose and common dolphins, the latter sometimes seen in "super schools" of 300-500 animals or more, while various species of whales and orcas are a relatively common sight. There are approximately 25 species of marine mammals in the gulf. Nearly a third of the world's marine mammal species live in or visit the Marine Park.Among larger cetaceans, Bryde's whales are residents and relatively common in the Gulf, and their presence in these busily