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EXPLORING THE WESTERN FRONTIER

THE MACKEREL ISLANDS

by Nigel Marsh and Helen Rose

 

All around us were fish – gropers, trevally, queenfish, sweetlips, snapper, rock cod, coral trout, angelfish, batfish, mackerel, reef sharks and stingrays. If that wasn’t enough we also had forty pairs of eyes staring at us, as we were being followed by forty inquisitive rankin cod. This dive site was one of the fishiest places we had ever seen, and the most amazing thing of all was this was the first time it had ever been dived! We called this site Rankin Road, and it was just one of many incredible dive sites we explored at the Mackerel Islands.

 

Until contacted by the Pilbrara Tourist Association we had never even heard of the Mackerel Islands. But checking a map we discovered the islands were located off Western Australia, near the town of Onslow, and just north of the famous Ningaloo Reef. With an invitation to explore the islands with a newly established dive operation on Thevenard Island, MI Dive, we headed west to the rugged Pilbara Region.

 

Getting to the Mackerel Islands from Brisbane was an adventure in itself. A flight to Perth, then a flight to Karratha, then a three hour drive, 300km south to Onslow, through the spectacular red soiled Pilbara. After overnighting at Onslow, we had the following morning to explore this small town, which has a very colourful history – including the whole town being relocated in 1926 and also being bombed by the Japanese during World War II.

 

By mid-afternoon we boarded The Specialist, a 12m long charter boat operated by Richard Burges, that was to be one of our dive boats for the week, for our crossing to Thevenard Island and the Club Thevenard resort. Thevenard Island is one of the ten islands that make up the Mackerel Islands and is 22km off Onslow. An hour later we arrived at the island and tied up at the pier. Greeting us were Dive Manger Greg Lowry, Island Manager Drew Norrish and Island Assistant Jamie Hornblow, who both assist Greg with dive operations.

 

Quickly unpacking, we were eager to get into the water; our first dive was to be at East Coral Gardens, off the eastern end of the island. We were diving in May and the water temperature was a lovely 26°C, unfortunately the visibility was only 2m, which was due to recent coral spawning and strong winds. Though the bottom was only 4m deep the coral growth, hard corals mainly, was thick and healthy and supported a good range of reef fish. We found blue spotted lagoon rays, boxfish, coral crabs, gobies, hermit crabs, tube worms and several interesting nudibranchs.

 

The next day we headed to nearby Trap Reef, diving a wall that dropped from 4m to 8m. The visibility was only 8m, but the dive was just amazing. The first dive hadn’t prepared us for the astonishing biodiversity in this area. The reef top was covered in hard corals, but the wall was encrusted in a wonderful array of spiky soft corals, sponges, hydroids, tubastra corals, ascidians and gorgonians – the colours just mind-blowing! The wall was also covered in nudibranchs, we had rarely seen so many in one spot. They were eating ascidians and many were mating. Nudies were to be one of the highlights of the Mackerel Islands; we saw at least twenty different species and must have seen over a hundred on some dives without really looking.

 

Exploring the wall we encountered white tip reef sharks, octopus, rock cods, coral trout and a wealth of other reef fish. Off the wall were bommies rising from the sand, some of these were swarming with schools of sweetlips and snapper. But a standout feature of this dive was a school of thread-fin pearl perch, a species generally only found in this part of Australia. We later dived another part of Trap Reef which was even better, with even more fish life, including gropers, trevally and a curious grey reef shark.

 

With the visibility a little limited we concentrated on macro for the first few days and found no shortage of subjects. At Sultan’s Reef, a large reef north east of Thevenard Island, we were going to dive a wall here but ended up on an unexplored coral garden with ledges and bommies to investigate. In 8 to 12m the coral growth was again rich and home to a great range of reef fish and invertebrates. The highlights of the dive being a crocodilefish, several sailfin catfish and a large olive sea snake.

 

The winds around the Mackerel Islands were very different to what we are used to on the east coast, most mornings we would wake to find a strong breeze which then dropped off to dead calm by lunch time. This meant that some of best dives were in the afternoon. One afternoon we explored the Thevenard Pier, which is not very long or deep, 4m maximum at high tide, but still fascinating. Many of the pylons are decorated with gorgonians and hard corals and shelter shrimps, crabs, cowries, lionfish, anemones plus anemonefish and many small reef fish. Squid are common at the pier and we watched three tiny squid catch even tinier baitfish!

 

By day three the water had started to clear, much to our relief. Greg, who has a lot of experience diving the Mackerel Islands, explained that the visibility is quite variable, averaging 12m to 15m, and affected by the winds and currents, which can be very strong around the islands. We dived two sites on the southern side of Thevenard Island with 10m visibility. The first was at Great Australian Bight, where an endless collection of bommies are found in 5 to 8m of water. We spent over an hour exploring these bommies, which are coloured by soft corals and gorgonians and home to lionfish, blennies, nudibranchs, octopus, shrimps, sea stars and some large crayfish. The fish life was as always incredible; schools of trevally, parrotfish, tuskfish, angelfish, sweetlips and Chinamen snapper.

 

At Rob’s Bommie we explored another set of bommies in 6m that were populated by schools of reef fish. But one bommie in particular kept us busy as it was covered in colourful corals and sheltered a sleeping tawny nurse shark and two northern wobbegongs.

 

With much of the Mackerel Islands unexplored, except by fishermen, there are still plenty of great dive sites awaiting to be discovered. We spent one day doing exploratory dives with Richard and Greg around Bessers Island. By now the visibility had improved to 15m, much more enjoyable for photography. Richard took us to a spot off the northwest end of the island, finding some interesting terrain on the sounder. Once anchored, we explored a series of coral ridges and bommies in 19m. The corals were as usual rich, and many of the bommies where swarming with cardinalfish. We found grey reef sharks, white tip reef sharks, a giant moray eel, coral trout, red emperor, coral cod, rankin cod and several estuary gropers. But the biggest surprise was a large potato cod that followed us for the entire dive. We nicknamed this site Tukula Corner.

 

We next dived a ridge off the northern end of the island in depths from 12m to 17m. This was another incredible dive with lovely corals and sponges, reef sharks, olive sea snakes, moray eels, schools of batfish and trevally, gropers, stingrays, mackerel and even a mantis shrimp. We also encountered three species of turtle – hawksbill, green and loggerhead – with the loggerhead puzzled by us and circling us for several minutes.

 

Our final exploratory dive at Bessers Island was on a group of large bommies in 15m, that we called The Scoops, as several of the bommies looked like giant scoops of ice cream. This was another lovely dive with pelagic and reef fish, reef sharks and even two mobula rays. After these three dives it was looking like you could jump in anywhere around the Mackerel Islands and guarantee a great dive.

 

Two of the top dive sites so far discovered at the Mackerel Islands are Greg’s Grotto and Black Flag. Greg’s Grotto is a maze of ledges, caves and swim-thrus in 14m and covered in a wealth of colourful corals. We just wish we had better visibility when we dived this site as the soft corals, sponges and gorgonians are just brilliant. But this site is also over-populated by invertebrates, reef fish and pelagic fish; common being white tip reef sharks, snapper, gropers, turtles, mackerel and lionfish.

 

We were lucky to have clearer water at Black Flag as this is without doubt the best dive site in the Mackerel Islands. As soon as we descended we were surrounded by an amazing number of fish – swarms of stripy snapper, batfish, baitfish, silver drummer and trevally. The reef here is 17m deep with the rocky reef riddled with caves, ledges, canyons and swim-thrus. The first swim-thru we explored was packed with sweetlips, mangrove jacks, bullseyes, cardinalfish and two large estuary gropers. We then swam through canyons seeing red emperor, coral trout, coral cod, rock cod, tuskfish, angelfish and Chinamen snapper. Exploring more of the reef we followed a ledge and encountered a dozen white tip reef sharks, several grey reef sharks, a tasselled wobbegong, a 2m long tawny nurse shark, turtles, stingrays and a fat scribbly pufferfish. There was just an endless parade of fish during the dive; a school of thread-fin pearl perch, mackerel, barracuda, jobfish and fusiliers. And if that wasn’t enough the reef itself was covered in incredible soft corals, gorgonians, sponges, hard corals and even black coral trees, and home to a wonderful range of invertebrate species. Greg was the first to dive this site and later informed us that he has also seen leopard sharks, bull sharks, sea snakes and Queensland gropers here. Black Flag is one of the most impressive dive sites we have ever done!

 

Our last day of diving at the Mackerel Islands came all too quickly, and with light winds and clear water it was a perfect day to do a few more exploratory dives. Our first stop was Brewis Reef. Richard found us some interesting terrain – a drop off from 4m to 9m and a series of bommies. With 15m visibility we explored a labyrinth of caves, arches and ledges which were all coloured by wonderful corals. We found two tasselled wobbegongs, several turtles, crayfish and the usual nudies. But the best part of the dive was the bommies, they rose from the bottom and were arranged like some ancient stone temple, and each was decorated with soft corals, sponges and gorgonians. And milling around them were schools of stripy snapper, sweetlips and fusiliers. As we explored the bommies we were buzzed by a grey reef shark and then a bull shark, and finally stampeded by a school of giant trevally. We called this site Stonehenge.

 

Our final dive was one of the best. With strong currents around the islands, the main reason they are so rich, Greg wanted to try a spot that could be done between the high and low tide, so we headed to a spot that Jamie had found fishing. This site featured a ledge dropping from 16m to the sand at 18m. We jumped in and found the current only mild and the visibility brilliant, 20m. It was quite a sight as we descended to the ledge, fish everywhere as mentioned in the introduction. The ledge was undercut by caves, but we were hard pressed to see this as it was overflowing with billions of cardinalfish. In and around the ledge were white tip reef sharks, estuary gropers, coral trout, coral cod, lionfish, sweetlips, angelfish and several barramundi cod. But the most amazing sight was the rankin cod. We had only ever seen a couple before, but here were at least forty of them, all staring at us. As we explored the ledge we also found a sleeping loggerhead turtle, a rare thorny stingray and several olive sea snakes, plus we had the rankin cod following us. As we swam along the ledge an endless procession of fish swam by; schools of trevally and queenfish, mackerel, Chinamen snapper and jobfish. We also found a crocodilefish, nudies, shrimps and the biggest hermit crab we have ever seen. This was one of the most amazing dive sites we have even explored. We called it Rankin Road and can see it becoming one of the top dive sites in Western Australia.

 

After a week of diving the Mackerel Islands we didn’t want to leave, as we still had many more great dive sites to discover. The only complaint we had about diving the Mackerel Islands was that the multitude of fish are so unfamiliar with divers that they were curious, but not curious enough to stay around for a photo!

 

CLUB THEV

Thevenard Islands is not quite your picture postcard tropical paradise; typical of this part of Australia the island is more like a desert with low scrub, red sand and a hot dry climate. Thevenard Island is a nature reserve and home to sea birds, lizards (no snakes) and an important nesting site for turtles. Located at the eastern end of the island is Club Thevenard, your home away from home while diving the Mackerel Islands. Now a word of warning, Club Thev is no Club Med. An ex-mining camp, the facilities are basic but comfortable and include 11 self-contained beach bungalows, 30 motel rooms, a pool, a games room, a dining room, a bar, a general store and a dive shop. Meals are included in the price, and while not extravagant, we found the meals delicious and filling. At the moment the resort caters for more fishermen, and oil workers, than divers, but hopefully that ratio will change with the dive operation in full swing.

 

DIVING IN AN OIL FIELD

The Mackerel Islands sit in the middle of Australia’s richest oil field, and the resort shares facilities, and the island, with a Chevron Texaco oil storage and refinery operation. Surrounding Thevenard Island are numerous oil rig pumping platforms, which look like they would offer interesting diving, unfortunately boats are not allowed within 100m of these platforms. The resort and Chevron work hand in hand, with Chevron providing water, electricity, an air strip and the pier that the resort can use. But the potential threat of an oil spill is always a concern, especially after the recent episode in the Gulf of Mexico. Plus we also learnt of plans to build a deep water port at Onslow that also has the potential to damage the delicate ecosystem in the area.

 

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