Life on Balmoral Net

The URG has undertaken a research project to monitor the re-growth of marine life on the newly replaced rope netting which encloses the Balmoral baths in Sydney harbour. The netting is often been visited by URG divers returning from boat dives. The site is an excellent location to “use up” the dregs of air in a scuba cylinder.

The nets main attraction is the resident community of sea horses. (White’s Seahorse –  Hippocampus whitei). These cute creatures are very delicate, yet agile as they swim through the net swinging from their tails. Refer to the Australian museum for further information on these creatures –

Two URG research tags have been placed at the eastern (seaward) side of the netting some two metres apart. The tags sit in about 2-3m of water. Over the coming months this site will be re-visited and a series of photo taken to form the basis of a longitudinal study.

Log of Observations

Colin Piper (who initiated this project) has kindly provided some background observations prior to the URG tags being placed onto the net in October 2001.

Apr 6, 2001Colin Piper counted 39 sea horses on the overall net. There were several large holes in the net from storms. This damaged net (the old one) being hung on the outside of the board walk which surrounds the pool. Colin reported seeing an angler fish on an earlier dive there as well not far seaward from the wharf
Aug 16, 2001There is a new net hung inside the old one. The new new net is the one presently in situ (on the inside of the boardwalk). It was very new and clean (i.e. no growth at all on it). Colin counted 73 sea horses on that dive, 55 were on the new net and VERY visible needless to say. The balance were on the old net.
Sep 21, 2001Colin counted 75 seahorses, all on the new net as the old one had been removed. Parts of it were lying on the sand with a considerable amount of fish life using the remains as shelter. The new net was no longer pristine. It was covered with the first stages of growth. There were also several new stainless steel retaining wires at various places around the pool. These were very shiny and new.
Oct 12, 2001It is estimated that the net has now been in place for about 3 months. Significant amounts of algae are now present. Prolific juvenile fish life move in and around the net. Two URG tags were installed on the eastern side of the net. No sea horses sighted between the tags, although about 20 where seen on the net overall. Significant pollution of the sea bed was evident (plastic bags, fishing nylon etc)
Oct 16, 2001Colin Piper counted 30 sea horses on the whole net this day The net was more covered and the stainless steel wires were also well covered. The latter was surprising because they were so clean only 31/2 weeks before. Most of the old net had been removed from the bottom.
Nov 18, 2001Dive completed following some light rain. Increased growth since November. Two sea horses were counted on the net panel containing the URG research tags. The general consensus of those who dived, was that the sea horse numbers are still less than compared to before the net was replaced. The harbour bottom around the net continues to be littered with rubbish, including a mobile phone. The "heavy metal" contamination from the leaking battery is of great concern.
Nov 30, 2001Robert Pearce and Colin counted 50 sea horses on the overall net. There was no specific count at the URG tag site. They noticed, and reported to a Council ranger that there was some damage to the net as a result of the large seas. This was when we heard about the possible removal of sea horses by people in the dead of night. Should this alarming news prove to be true, it is more important than every to continue to monitor this site.
Dec 22, 2001Click the link to the right to download and view this short movie of a local sea horse dining out on the net. Watch very carefully after the prey is eaten and you will note the sea horse "exhausts" a milky liquid from the back of its head. Cool!

Only one sea horses at the URG tag site. Further counts later in the month 28/12/2001, recorded only two sea horses.
Dec 28, 2001Colin observed 2 at the URG tag site. Colin also noted that it appears that the sea horses are more abundant on the sheltered sides of the net. (i.e Not on the sea-ward facing areas).
Jan 1, 2002A late evening dive recorded zero sea horses at the tags. There had been some very large tidal movements, and at one stage approximately half the net had been exposed at low tide. Algae growth on the net is rapid in the warm summer water. The URG tags placed in October had to be cleaned to remove excessive growth.
Jan 28, 2002On an early morning dive, David Oatley counted 22 seahorses on the entire net, none at the URG tag site. Colin Piper's earlier hypothesis about there being unequal distribution was proved true. (Refer diagram on right). Twenty seahorses on the section indicated with red arrows and, two on the remainder of the net.

Note the level of marine growth in photo A from the northern side. The URG tag site has markedly less growth in which the seahorse may shelter. Photo B - Some of the other marine animals spotted on this dive.
Mar 3, 2002"Clean up Australia Day" was conducted today at Balmoral. The URG removed a significant quantity or rubbish including plastic bags, fishing rods, milk crates an even a shopping trolley. A less than thorough count was conducted with only about 12 seahorses seen, with 1 at the tag site. A more complete count will be done later this month.
Greenwich BathsMember Simon Dakin took this image at Greenwich baths during February. Note the water colour Thanks Simon! Please visit to see more of Simon's work
Mar 10, 2002A small group of URG divers drop in for a count, following a morning dive elsewhere. Only 5 seahorses were counted from the beach east to the URG tag site. Zero were at the tags. The net panel at the tag site has very little growth, and hence the zero count is not surprising. A key question is why there is such as unequal distribution of growth around the perimeter? Three theories exist (if you have one let us know!):-

(a) Large recent influx of fresh water from rain has purged the net.

(b) There is a prevailing current around the bay which "ventilates" one side of the net more than another.

(c) The URG tag site is close to, and faces a cluster of moored boats. Could the anti-fouling paint be leeching and stripping the growth from the net in this area?

Time to start some experimentation!!
Apr 1, 2002Four divers were unable to positively locate the tag site on the net. The green stinger net seems to have collapsed down the main netting. Either the tags have been removed, or are now obscured by the stinger net. No seahorses were counted near the tag site, this probably being due to the stinger net smothering the main net.

Eight seahorses were counted from the tag site back to the beach, via the wharf. Colin Piper has the treat on witnessing a marine bird swimming underwater with him.
Apr 10, 2002Colin Piper did a count sea horse count this day. Colin was joined by Tina Brain, so it was a very accurate count. They did it from INSIDE the net…much easier to see the critters, and made it possible to see the net which is usually hidden/obscured by the stinger net.

Between the beach and the wharf they counted 5. In the area of the wharf and the northern swimming platform there were 14. Between there and the corresponding swimming platform on the southern side there were 9. None were seen on the URG tag site. Between the southern swim platform and the beach there were 9

In total, 37 were counted. There were a couple which appeared to have, they were pretty 'swolen'. Both in the wharf area. There were a few very small ones, and one was quite big…interestingly enough…this one was near the URG site.

Last year on April 6th Colin counted 39 in all. Taking the same area counted, this year there were 34. This is the first time that there has ever been a proper count on the southern side of the pool, where there were only 3 .

The net is mostly well covered with growth…though I leave those observations to others more qualified than I am to comment. The stinger net has the effect of 'rubbing' clean the upper part of the actual net very visible from inside the pool.

Colin recommended that we always count from inside the net in future, as it is so much easier to see the seahorses.
May 5, 2002A partial circuit of the net was made following a dive elsewhere. This quick dive started at the tag site and proceeded south. The tags are covered in fine barnacles, but the net is very clean in terms of algae, with no seahorses being present. Only one other was seen on the swim to the boatshed.
Jul 6, 200236 seahorses around the net perimeter. The tag site could not be found. Last month the tags were totally un-readable, so they may just been missed.

The net is very badly damaged. There are holes larger enough for a divers to swim through easily. We will inform Mosman Council. The seas last week where very big!
Sep 5, 2002Colin Piper

I did a sea horse count this morning at Balmoral. It was sunny with very clear water and it was very still. I did it from INSIDE the pool because it is then possible to see that part of the net which is usually obscured by the stinger net. With one pair of eyes, in 71 minutes, the results are as follows; Starting from in front of 'Watermark'. Between the beach and the wharf area, I counted 6. In the area of the wharf and the northern swimming platform there were 14; seven of these were all quite close together. Between there and the corresponding swimming platform on the southern side there were 8.

I could not locate the URG tag, although I looked long and hard for it. There is a new "patch" in that area, as the original net is very damaged, presumably from heavy swells in the past few months. There are also 2 holes large enough to swim through with ease. Between the southern swim platform and the beach near the boatshed, there were 5. In total 33 were counted. That is not to say of course that there weren't more. Two or three pairs of eyes are always better than one!

The overall condition of the nets, (both the shark net and the stinger net), is deteriorating and I can imagine that it will be replaced within the next 6 months. It might be worth the URG asking Mosman Council what they propose, so that the population of seahorses might be "saved" when the inevitable replacement work is done.

Many of the stainless steel braces, which were installed with the current net (middle of 2001) have broken away, and those that haven't, have made holes in the net from rubbing action. Those familiar with the Balmoral net will remember that the old net was attached to the outside of the swimming enclosure, and the replacement in 2001 is attached further inside the section of the walkway, which runs around the pool. There is a considerable amount of growth in some areas of the net…weighing it down in some places. The stinger net is also very close to the shark net in some areas (rubbing against it) and in other places it is a metre or more away. Some of these areas are un-attached and just wave in the current. This makes it difficult, and probably a bit dangerous to now attempt a proper count from outside the enclosure. In any case, I am convinced that inside the pool is the most accurate way to count.
Sep 24, 2002Along with new committee member Robyn Stevens, Colin Piper did another sea horse count this morning at Balmoral, as last time, from inside the net:

  • Total time 55 minutes.
  • Starting from in front of 'Watermark' Between the beach and the northern swimming platform 25 were counted.
  • Between there and the corresponding swimming platform on the southern side - 21.
  • Between the southern swim platform and the beach 8 counted. 54 counted in all
The 2 large holes noticed on Sep 5th have been repaired. The large specimen was again seen in the URG tag area…and another large one was seen between there and the wharf as well. There were more counted this time, but not only because there were 2 sets of eyes…I certainly noticed more. There was one small one in only a few feet of water very near the beach where we started. It was high.
Dec 19, 2002Simon Dakin and Colin Piper did another sea horse as last time, from inside the net. Total time 80 minutes. High tide. Starting from in front of 'Watermark'

  • Between the beach and the northern swimming platform we counted 15.
  • We observed 2 which were heavily pregnant.
  • Around the platform/wharf area we counted 52, only 2 of which were in the upper half of the net.
  • Between there and the corresponding swimming platform on the southern side we counted 29. (six of these in the upper half).
  • Only three of the twenty nine were in the southern half of the 'eastern side of the pool.
  • Around the southern swim platform we counted 8 Between the southern swim platform and the beach we counted 3.
  • We counted 107 in all.
Interestingly, around the wharf/swim platform area we saw several 'couples' for want of a better word. I have never previously seen sea horses in this 'courting' mode, if this is indeed what they were doing.

Neither of us saw the large specimen in the URG tag area…no sign of the tag either.
Jan 24, 2003Simon Dakin - Dive time was 100 minutes. Weather was sunny, sea was calm and tide was coming in and about high at end of dive.

  • 65 White's Seahorses
  • Big-belly Seahorses
    Feb 5, 2003Simon Dakin/Colin Piper from inside the net. 53 seahorses counted in all.

    • Between the beach and the northern swimming platform - 15.
    • Around the platform/wharf area - 20
    • Between wharf & swimming platform on the southern side - 14
    • Around the southern swim platform - 8
    Much of the stinger net is 100% covered with growth.We didn't complete the count on the Southern side…we swam across the pool on the bottom looking to see if caulerpa taxifolia was evident on that particular "transect". It wasn't. We did see a seahorse in some growth well away from the net.
    Mar 27, 2003Simon Dakin and Colin Piper did another sea horse count at Balmoral from inside the net. Total time 75 minutes. Low tide. Excellent visibility.

    • Between the beach and the northern swimming platform we counted 10.
    • Around the platform/wharf area we counted 27
    • Between there and the corresponding swimming platform on the southern side we counted 20.
    • Around the southern swim platform we counted 5.
    • Between the southern swim platform and the beach we counted 4.
    • 66 counted in all. Six of these were Big bellied sea horses.
    Jun 4, 2003Simon Dakin completed a 107 minute dive & counted 61 seahorses. All were Whites with no Big Belly seahorses seen at all. The greatest concentration was around the dock area. I saw a juvenile, perhaps 10cm long (including tail) and one seahorse anchored on some seagrass just away from the nets.
    The stinger net continues to decay, a large section having fell to the seabed on the left hand side and there are now some huge holes in the net itself in the central section, quite big enough for divers, let alone sharks to swim through.

    The central section carries more weed than ever and in the areas it was difficult to get a good count. Where the upper section is still in place it was quite dark whereas at the bottom where the stinger net finished it was very bright with the sun behind and it was a struggle for the eyes to repeatedly adjust to the the very differing light levels. As a consequence I suspect the count is quite an underestimate.

    Notable amongst other fauna, I saw a big crab on one of the piers, a Gunters Butterflyfish, a couple of what I suspect where Dusky Butterflyfish and a school of juvenile Striped Catfish in between the stinger and main net.

    In the middle of the dive I heard a police siren and someone talking. Most pecular. Whilst I was inhaling and exhaling it was difficult to make out words but whilst having a rest on the bottom I heard phrases such as "Number one, I'm getting no readings" and "clear your regulator". After the dive I had a stroll along the boardwalk and far away (hundred of metres) I could see a dive flag on a boat moored to the wharf at HMAS Penguin. I presume they were using underwater speakers to communicate to divers. Not sure what they were up to but as I was looking 3 camouflaged Apache helicopters came in to land at the base.
    Aug 15, 2003On August 15th, Mark Robinson and I did a sea horse count at Balmoral from inside the net. Total time 59 minutes. High tide. Reasonable visibility. Fifteen degree water.

    • Starting from in front of 'Watermark'
    • Between the beach and the wharf area we counted 26.
    • Between there and the swimming platform on the southern side we counted 83.
    • Between the southern swim platform and the beach we counted 10.
    • We counted 119 in all.
    This is the highest count I have had since starting seriously in April 01. The net has many repairs evident, Simon Dakin reported large holes on his count in June I think. Two sets of eyes make this a reasonably accurate census I think, though as always, they are hard to spot, especially where there is considerable growth on the net.

    Colin Piper