Sharks and Rays
Did you hear about the extremely rare magpie fiddler ray Trygonorrhina melaleuca caught by fishermen in the Port River last week? There is a nice item about it on the ABC website (see link below), including an interview SARDI researcher Paul Rogers who is making some observations on the ray before releasing it back into the Port River at the request of the anglers who caught her.
This story is significant for many reasons.
1. This is a ray that has only ever been seen a few times before, and yet still exists – in the Port River – and we know so little about it!
2. It reminds us that there are many species that are unknown or not well understood, and that opportunities to learn more about them are valuable.
3. The anglers who caught the ray (from the Adelaide Game Fishers Club) recognised that they had caught something special, contacted SARDI and have requested that the ray be released back into the river.
4. It adds weight to the argument for protection of biodiversity in the Port River, which clearly supports some interesting species, despite being a busy industrial area.
There are a few types of eggs or egg masses that are easy to recognize on the beach. Considering how many marine animals actually lay eggs, it is a bit surprising how few we see regularly!
The egg mass produced by a couple of species of the moon snail (Polinices conicus and P sordidus) is often mistaken for a jellyfish. That’s because you can barely see the miniscule eggs, but they are held in a transparent, firm, sausage-shaped jelly matrix. They start to appear on the beach in spring.
Squid eggs are also easy to recognize because they are soft, whitish and clumped together in a bunch.
The most common shark egg cases we find locally are those of either the Port Jackson sharks or skates. They are dark brown, rubbery and shiny when fresh, but when hatched or dry become hard brittle. The Port Jackson shark egg case is spiral shaped, tapering from the base to the tip. Skate egg cases are shaped like small pillows, with tendrils on each corner.