Cabbage Tree Bay

Cabbage Tree Bay, Manly: a 1:1000 scale map of the aquatic reserve, free to download as a PDF or a high resolution bitmap.

The aquatic reserve at Manly, mapped at 1:1000 — in a photo editor, one millimetre is one metre. GPS positions are WGS84 throughout.

Conditions today: this site is CTB Bower Lane on the VIZ Forecast.

The Cabbage Tree Bay map

The site is described in several places, including Michael McFadyen's website. What you will find here is the most current map. For the life in it, John Sear keeps a list of all 360 species recorded in the bay.

Weedyland, and what happened to it

As of January 2023 the weedy seadragon colony appears to have gone, after the big swell of March 2022 when more than a hundred were found washed up between Manly and Mona Vale. Where a single dive once found up to five, the chance of seeing one now is close to zero — one individual has been reported since.

The map would not normally show precise sighting locations; they were protected behind the general "Weedyland" area. Since those sightings are no longer current, the stars are now shown as a matter of record.

What else is down there

Pocillopora aliciae. Universities including UTS have coral survey sites on the ocean side of the bay. The first specimens were found here around 2012 by John Sear; by 2023 they had spread across the north and east of the headland, with one inside the bay. Another Sydney colony was found at Dobroyd Head in June 2022 — currently the southernmost recorded on iNaturalist.

Acoustic receivers are scattered around the bay. Similar ones were used for a study of tagged wobbegongs between 2008 and 2013 — the paper is here.

Goggles Graveyard was named in January 2023, on realising that the rubbish in the bay all ends up in the same place, and that most of it is goggles.

The big picture

From SEED, the NSW Government's bathymetry.

The SEED bathymetry of Cabbage Tree Bay

Points of interest on the map

A weedy seadragon Motorbike 1 · −33.799318, 151.295836 Motorbike 2 · −33.798606, 151.295833 The Big Cube · roughly 3 m across and more cubical than it looks here. Magnetic north for 50 m from it puts you in Weedyland. −33.798315, 151.296285 Dragon Tooth · a distinctive rock pointing up, in 6 m Stargazer Rock · 6.5 m, 58 m past the Big Cube, another pointer to Weedyland. −33.798058, 151.296793 Acoustic receiver 3 · the pole is covered in kelp Acoustic receiver 4 · the pole is covered in kelp Acoustic receiver 2 · the pole is covered in kelp The Big Dick · points at the smaller of the two Deep Reefs. −33.797908, 151.295545 The Arch · about 3 m long, standing 30 cm off the floor. −33.798796, 151.295821 A length of empty plastic pipe, recently emerged from the sand Sarah · a Yamaha 15 HP outboard at 13 m. −33.797003, 151.296911 Acoustic receiver 1 · a data recorder tracking large fish carrying acoustic tags. −33.798553, 151.295093

All depths are at zero tide — add the tide of the day.

Where the mapping started

This is the first version of the map, from July 2020, and the beginning of the whole business.

The first version of the map, July 2020