By Toufiek Samaai, Sven Kerwath, Albrech Götz, Chris Wilke and Charlene Da Silva

In April 2009, five marine scientists and three technicians spent two weeks on the Research Vessel, Ellen Khuzwayo on the Agulhas Bank. Chris Wilke, diving supervisor, mariner (skipper!), ship figurehead (Mr. Wilke) and dive chamber technician facilitated a total of 10 man dives on the reef and pinnacle habitats of the Alphards Bank and 12 Mile Bank. The group comprised of a team of marine ecologists (fish experts) from MCM, an ecosystem monitoring expert and fish ecologist from SAEON, a sponge (benthic) systematist and a shark biologist from MCM.  Armed with a research ship, long lines, fish cages, dredges, CTDs, several cameras, collecting bags (or bottles), diving equipment, diving chamber and more enthusiasm than air, we prepared ourselves for our research adventure in discovering what lives on the hard reefs off the Agulhas Bank by documenting habitats and collecting fish, sharks, seaweed, sponges, echinoderms, sea anemones and bryozoans that live there. 

Bathymetric map of part of the studied area on the Agulhas Bank showing Martha’s Reef, 12-Mile and Alphard Bank. So far, very little bathymetric information is available on the two additional research sites 45- and 72-Mile Bank (therefore not shown here).

The collaboration between the fish, shark and benthic ecologists was initiated by Dr Sven Kerwath (MCM) with the aim of understanding the diversity of benthic invertebrates and severely overexploited line fish and shark species on the Agulhas hard benthic banks. This project worked closely with marine scientists from SAEON and has played a critical role in evaluating methods for Long-Term Ecological Research and Monitoring (LTERM). This was the second time after the initial survey in 1987 that Alphards Bank and 12 Mile Bank had been dived or surveyed and a surprising diversity of habitats and species were uncovered especially amongst the benthic fauna. Faced with a bewildering array of taxa, we catalogued them in the different taxonomic groups to build on studies documenting offshore biodiversity on the Agulhas Bank.

One of the interesting discoveries of this trip was the diversity of benthic and fish communities on these mixed substrata and hard reef habitats, particularly on 72 Mile Bank, 45 Mile Bank and Alphards Bank. The finds that caused the most excitement were the capture of a 2 meter juvenile seven (7) gill cow shark and small stalked medusa like sponges that stood 1 cm tall attached to rubble & rock fragments in a soft-bottom habitat at depths of 80-100 m. This seems to be a new species of Asbestopluma, a carnivorous sponge genus, and on the list of priorities was to document and take the in-situ photographs for the field guide that sponge-bob is presently working on. During the first dive at Alphards Bank, Sven, Charlene and Chris landed on the edge of the pinnacle at 43 meters where they started with their fish point counts. They were not disappointed, because just beyond the sampling point off the pinnacle the reef falls steeply away into unfathomable depths, leaving much to their imagination.   On the second dive, Ali and I ventured alone with our cameras and plastic bags and discovered all sorts of new and exciting benthic things that we documented, photographed and collected.  It was on this dive that we discovered the illusive green latrunculid sponge that may hold the cure to cancer, TB or HIV and "German invasive species".  

A fish trap is recovered by the crew (left). Fish traps are very effective when targeting a broad spectrum of demersal reef fish including catsharks (right).

On the last day, some of us reluctant to fish and long line conducted a last dive inshore of 12 Mile Bank. We returned with some amazing benthic critters that were sorted, labeled and bagged with trepidation and a further workup in the lab. In total some 278 specimens of benthic invertebrates were collected. As their identification is largely dependent on skeletal morphology, they can only be reliably identified in a well-equipped lab and by consulting all the available literature. Much to the annoyance of Sven who kept on asking for immediate identifications of the collected benthic critters, Toufiek continually recited the almanac of this legitimate line of reasoning.

The trip however, was not without its ups and downs, some of us got sea sick, and some of us got the flu, while some of us even picked up the pink eye.  Despite our illnesses we set the long lines and fish traps and divers even returned to the waters to do some more fish counts; we counted and caught red stumpnose, carpenter, hottentot, blue hottentot, roman and a few shark species. Further investigation of the otholiths (calcareous ear piece skeletal elements found in fish), gonads and fin clips (for genetics) that we removed, in our make shift fish lab, will bring certainty towards the maturity, age and population structure of the many fish species we collected. In total some 1000 fish were collected many of which were filleted after we have finished off all the biologicals on them. 

Fish captures by traps are being measured (left) and dissected to remove gonads and otoliths (right).

During the two weeks 278 invertebrate specimens (e.g. 200 sponge specimens and 35 bryozoan specimens) were collected and “Sponge Bob” was busy in the lab taking photos, preserving samples and educating his colleagues on the art of sponge taxonomy.  Sven cringed every time he asked “is this a sponge, what sort of sponge is that”, and Toufiek would answer, it’s a species of hmmmm, I have no idea and with excitement he would also say, this looks like a new one, never saw this before.  One needs to be a “Sherlock Holmes” to piece together the clues to solve the species identification.  This is much to the annoyance on Sven, who is no sleuth.  His venture on this trip was one of discovery and excitement, as for every specimen he sampled and preserved, made him realized that we know little of the Agulhas Bank fauna in terms of the diversity of benthic sessile invertebrates. The benthic diversity on the Banks were astonishing in their numbers, taxonomic diversity and the assemblages come in a multitude of shapes, sizes and colours: some looked like elephant ears, or tree branches, while others looked like flat mats, vases or medusa heads.  What became evident on this trip is that there is still so much that we don’t know, but what we see never fail to stimulate the imagination and wonder at their extreme beauty and diversity. 

Invertebrate (left) and fish (right) communities on Alphards Bank

Aside from the exciting science, supper in the mess as well as the times spend around the PCs, afforded us the opportunity to share ideas. Describing biodiversity and drawing up baseline check lists is a necessary step towards understanding South Africa’s unique marine biodiversity which in turn is essential for management and conservation. 

Building on the foundation laid during this voyage, we hope to continue this work during our next cruise in the winter season of 2009 when additional attention will be turned to further develop suitable invertebrate sampling methods, deploy a remotely operated vehicle (ROV) and a baited underwater video camera (BRUV).