SCUBA News (ISSN 1476-8011)
Issue 255 - September 2021
Welcome to SCUBA News - thank you very much for subscribing. For readers in the UK some good news this week: previously out-of-bound diving destinations, such as Egypt, Oman, the Maldives and Turkey, have been removed from the UK's Red List. When you return from these countries you will no longer have to quarantine in a hotel for 11 nights.
A marine park entirely encircles Saba's rocky coast in the northern Caribbean, and there is some outstanding diving there.
The best time to dive Jordan's Red Sea is in October and November for healthy corals, fish & turtles.
Blue Force 2 visits some of the best reefs and wrecks of the northern Red Sea.
Trigger fish have deep bodies, high eyes, small mounths and colourful patterns - no more so than the Picasso Trigger Fish.
Five of the six species of the Rhinecanthus genus are known as Picasso Triggerfish (or just Picasso Fish). They are all between 23 and 30 cm long and mostly live in shallow water, less than 20 m deep. You will find them on the reefs of the Red Sea, Arabian Gulf, Great Barrier Reef, Pacific and Indian Oceans. As adults they are mainly solitary, but the young fish may live in schools.
Picasso triggerfish feed on a wide variety of animals living on the bottom: fish, invertebrates and algae. To find worms to eat they will blow a jet of water to move the sand. They like sea urchins and will upturn them to avoid the spines before eating. The triggerfish's eyes are very high up, which may be to prevent them getting spiked the tasty urchins. Rhinecanthus sees in colour and studies show it prefers red food, followed by green.
Blackbelly Picasso Trigger Fish, Rhinecanthus verrucosus, Indo-West Pacific. Photo credit: Bedo, (CC BY-SA 4.0)
An attractive fish with blocks of colour on a white and beige background. Unlike some trigger fish, these aren't commonly aggressive towards divers.
Reef Picasso Trigger Fish, Rhinecanthus rectangulus, taken in Hanauma Bay, Hawaii. Photo credit: Qyd
Trigger fishes are so called because of the shark-fin shaped trigger they are able to raise in defense. They use this to jam themselves into a crevice in the coral. The trigger is actually the first spine of its dorsal (top) fin. They bend the second spine forward to fix the first firmly in position. When the fish is swimming the fin is flattened into a groove.
Triggerfish are territorial. Some picasso triggerfish maintain their territories for more than 8 years. For R. aculeatus, each male territory overlaps 2 or 3 female territories. The females lay their eggs in nests on the sea bed and guard them well. It is more usual for male fish to protect eggs, but as one male mates with each of the females on overlapping territories, less eggs would be fertilised if the male spent his time "standing" guard.
Lagoon Picasso Trigger Fish, Rhinecanthus aculeatus, Indo-Pacific. Photo credit: Arpingstone
Class: Actinopterygii > Order: Tetraodontiformes > Family: Balistidae > Genus: Rhinecanthus
For more featured creatures see the marine life highlights.
Coral Reef Fishes, Indo-Pacific and Caribbean, by Ewald Lieske and Robert Myers, Harper Collins
Part I, Fishes, by Farid S Atiya, Elias Modern Printing House, 1994
Cheyney et al. (2013). Colour vision and response bias in a coral reef fish. J Exp Biol. 216 (15): 2967-2973.
Tetsuo Kuwamura. (2010). Evolution of Female Egg Care in Haremic Triggerfish, Rhinecanthus aculeatus. J. Ethology.
Enter Now: Ocean Art 2021 Underwater Photo Competition
Travel opens up from UK to top diving areas like Egypt and the Maldives
Coral reefs are 50% less able to provide food, jobs, and climate protection than in 1950s, putting millions at risk
Loggerhead turtles born as far north as Venice
Ecuador eyes new Galapagos marine reserve to limit commercial fishing
Instructor fined after pupil dies in deep water dive to find German submarine
Indonesia's newly minted investigators to go after illegal fishing kingpins
Basking sharks disappearing from Isle of Man but congregating off Ireland
Some coral reefs can keep up with ocean warming
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Photo credits: Tim Nicholson, Jill Studholme, Kristin Riser, Jianye Sui
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