MV Hallelujah Trip #31 28 Mar – 1 Apr 2018 | Top of The Chain

Diving the Similans, Koh Tachai and Richelieu Rock this season there has been a very noticeable increase in productivity on many Simillan dive sites. Richelieu has its resident über mob of juvenile Giant trevallies and Longnose emperors. Koh Tachai, when the current pumps so do the Bluefin trevally and Rainbow runners.

All around the Similans there are more dog tooth tuna, snapper and other types of predatory fish. There are a few possible reasons why we are seeing more bigger fish on our dive sites. There is also a number of contenders in the running for top predator of 2018.

Predatory barracuda in the Similan IslandsSadly, for the Similan Islands, it is because of the absence of sharks that there’s now an opening for other predatory fish to dominate the top of the food chain. Fish aggregation devices close to national park boundaries and a chequered past of fishing with large fish traps around dive sites has decimated shark populations.

There is hope though, which leads us nicely into one of the reasons why we are seeing more predatory fish around our dive sites.

Similan National Park Management

Glass fish provide food for predatory fish in the Similan IslandsSince Mr Ruamsilp took over the reigns as a Similan National Park chief a couple of years ago there has been a vast improvement in park management. The park’s natural resources are better protected, both above and below the ocean surface.

An unprecedented rise in park entrance fees suggest corruption is also well under control and revenue is being used to better police the park and provide visitors better facilities. Despite the absence of sharks the general consensus amongst local dive professionals report that there is a noticeable rise in predatory fish life.

Coral Recovery

Small reef fish occupy healthy coralsWith the ongoing recovery of numerous hard coral species on many Similan dive sites there is also the expected increase in fish species that use these corals for protection. Even during the leaner post bleaching seasons the dead corals provide some shelter to smaller reef fish. This season has season an explosion in colourful reef dwellers such as Basslets, Blennies, Damsel fish and Gobies

The healthier coral reefs also serve as protection for glass fish, again more noticeable in greater numbers this season, especially at Richelieu Rock. More ‘bait’ or glass fish and more small reef fish around the Similan reefs seems the attract and support the larger quantities of predators.

The More Cynical View

Whale shark at Richelieu RockAs the 2017-2918 Similan diving season draws to a close we are also presented with another reason for increased numbers of larger fish. This view has been hawked around since my earliest years working at the Similan Islands.

With the presence of so many dive boats around, fishermen are less likely to drop fish traps and nets close to the reefs. So as a season progresses the quantity of fish stocks so too increases. A valid point but hopefully with the improvements in park management fish stocks will remain when the Similans close in May 2018. Richelieu Rock was closed to divers in May 2017 during a period of high productivity. When it reopened in October 2017 there was no noticeable drop in fish stocks.

2018’s Top Predator

The current was pumping during our sunset dive on Richelieu Rock. It was possibly the strongest current I have dived in there during the season and most dive groups were sheltering on the outside, deeper side of the rock. Luckily, diving with Lia and Jacque we were able to beat the rising tide and also dive the shallower inside areas of Richelieu.

What we encountered I can only describe as fish Armageddon. All manner of fish were struggling in the current and the juvenile Giant trevally were making the most of it. Instead of schooling and hunting the trevally has split into twos and threes and were everywhere, everywhere and causing havoc.

hunting trevally at Richelieu Rock
Image @ Lia Barrett –

Everything scattered out of their way, even the menacing, dangerous Pick-handle (42 stitch) barracuda were twitchy choosing the relative safety of shallower water rather than getting in the way of the hunting trevally. And remember these are just juveniles.

So for me, right now the Giant trevally are sitting at the top of the food chain, the Similan’s apex predator. Though I do rather prefer to think of these fish as just the caretakers of the food chain, sitting in until our sharks return. Fingers crossed with continued improved park management sharks will make a come back and take back their crown.

MV Hallelujah Similan Liveaboard Trip 31

Group photo Similan liveaboard trip 31Boots, Lia, Ric and Jacque

A big (blue) thank you to all our guests who joined us for trip 31. Special thanks to Lia from all the crew on Hallelujah, we have all been proudly sporting our amazing Prawno gear ever since. Lia Barrett is the Creative Director at Prawno Apparel and Photo Editor for She’s also one of my best dive buddies, having dived together in the Similan Islands since the early days of our careers. Lia’s one of the few who inspire me and it was an absolute pleasure to dive with you and Jacque on this trip 🙂

You can read Lia’s article about our trip on MV Hallelujah here.