Tag Archives: starfish

South Australia’s Fleurieu Peninsula underwater

2 Dec

Dear Reader:

 I am snorkelling along the edge of the reef just off Aldinga Beach. The water is shallow and warm with just a light breeze ruffling the surface. Below me the terrain changes from seagrass to sand with a little outcrop of rocky reef in between and I am intent on photographing the variety of marine organisms that inhabit these different habitats.

 

A patch of reef near the seagrass beds

 

The reef has numerous invertebrates clinging to, and encrusting its wide variety of niches and a biscuit star is my first sighting. This pentagonal little seastar can be found on reefs and rocky surfaces and has a number of colour variations between light orange to reddish. It has quite large overlapping plates on its surface and has an arm radius up to 7cms.

 

Biscuit star alongside sea snail on reef

 

Leaving the little patch of reef behind I start to scour the seagrass bed where it meets the sand patches. My choice of location pays dividends as I disturb a blue swimmer crab that has been hunting in the seagrass.

 

Blue swimmer crab does not want to be photographed

 

Blue swimmer crabs have large pincers on their two front legs and paddles on the rear pair. They can be seen moving along the bottom in weedy and sandy areas but often bury themselves in the soft sand and mud. These large crabs can be quite aggressive when approached and feed on live animals as well as scavenging. They are migratory appearing from September to April in SA waters. Taking female Blue Swimmer Crabs with eggs and animals under 11 cms is illegal and there is a personal bag limit of 20 crabs per day. These restrictions help preserve the numbers of this commercially and recreationally valuable species.

These invertebrates are just two of my many encounters on the reef and the bushland around the Fleurieu Peninsula and I shall continue this story in my next post.

Cheers

Baz

Notes:

Over the next few months I will be writing a book about the wildlife of the Fleurieu Peninsula. My posts will reflect the research I am doing and provide more detailed information about each animal that I encounter.

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Life Under the Port Noarlunga Jetty

21 Jan

Dear reader

This week has been hot with temperatures hovering around the mid 30s- perfect weather for a dip in the ocean. Although our urban beaches are perfect for swimming it is the more rugged coastline further south that always attracts my attention. As a keen snorkeler and underwater photographer the cliffs, headlands and rocky reefs, interspersed with fine, sandy beaches, create a tempting environment for anyone interested in marine life.

Port Noarlnga jetty showing growth of mussels and beach

Port Noarlnga jetty showing growth of mussels and beach

Consequently, last Saturday morning found me donning my summer wet suit and sliding into the water under the Port Noarlunga jetty; a favourite dive location only a 45 minute drive south of Adelaide’s CBD. Like many of South Australia’s jetties; this one is the legacy of bygone days when wooden ketches collected grain from coastal farming communities. The old wooden structure juts out from a sheltered beach and is sandwiched between low limestone cliffs and an estuary. Two hundred metres out to sea it intersects a reef that runs parallel to the shore. Although the reef is a marine sanctuary there is limited fishing allowed along the first three quarters of the jetty. Most divers go to the end of the jetty and drop straight onto the reef. However, on this occasion I had decided to swim under the jetty and look at the way the environment and marine life changes with depth and proximity to the reef.

starfish on jetty pile amongst coraline algae and green algae red

Starfish on jetty pile amongst coraline algae and green algae

 The first few metres were quite a surprise. I had expected bare sand and little life. Instead I found quite a community of organisms in the shallow warm water. Small schools of mullet and yellowfin-whiting and some bream were patrolling the sandy bottom searching for small crustaceans and worms. A few large razorfish, a fan shaped mollusc that buries its pointed end in the sand, protruded amongst the small outcrops of rock and sparse seagrass patches while several sand crabs scuttled for cover in the weed as I swam over them.

Razorfish amongst seagrass

Razorfish amongst seagrass

In the shallow zone, the jetty piles are constantly exposed to air and sun as the tides and winds vary. Only a few grey snail shells and worm tubes clung to them finding moisture and protection in the cracks in the wood. As the water became deeper a coating of small black mussels shaded the grey wood of the piles and a mixed growth of algae, sea squirts, sponges and other encrusting organisms started to appear. In the open water schools of baitfish would occasionally appear in tightly choreographed formations; a group strategy evolved for minimising successful attacks by predators. Closer to the surface, I caught sight of the occasional garfish and even a small group of squid chasing after a fisherman’s lure.

Squid in open water following lure

Squid in open water near the jetty attracted by angling lures

As I approached the end of the jetty, the character of the environment changed dramatically. The growth of invertebrates covering the wooden supports had thickened and a veritable garden of different organisms of every texture and colour imaginable competed for space and food. Small patterned fish and shrimps darted amongst these marine jungles and an occasional starfish also moved slowly though them in search of prey. The baitfish had been replaced by a mixed school of sea sweep and old wives.

School of sea sweep with a few striped old wives

School of sea sweep with a few striped old wives in the background

When I reached the end of the jetty I used the aluminium dive ladder to climb out and sat for a while on the wooden walkway and watched a few divers exploring the reef. A quick glance at my dive watch indicated that I had been in the water for well over an hour. The time had passed quickly and I had been more than pleasantly surprised by the marine life under the jetty….worth another visit.

Cheers

Baz

Baz

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