Fishing Management at Zandvlei...

**BuzzLiteBeer** · 06-04-12

From Anton Ressel....

I was just down there at about 7.30, water was flowing out fast and with it many fish trying to get out, mainly small to medium steenbras and some leeries, but apparently there were kob before I got there. One large kob died after getting stranded in the shallows, probably 8kg or so.

We were running the fish that got stuck on the shallow banks near the shore trying to get out, back into the sea. Nature conservation were there and law enforcement (who looked more bemused than concerned), and about 5 guys running the fish out, using thrownets and bare hands to catch and release them. Chris Fallows was doing a huge job, as was Mark Stoatesbury and some other guys. Also some lurkers around, rest assured the moment backs are turned stranded fish will be taken.

Anyone who can get down there will be welcome, I have been 3 times today already but have guests now, please help if you can at whatever hour.

Regards
Anton

**BuzzLiteBeer** · 08-04-12

From Chris "Airjaws" Fallows....

Yesterdays rains seem to have helped the fish side of the problem as last night and this morning the water was pushing strongly out of the vlei. Also Cassandra and her team were there again last night making sure nobody poached fish. Hopefully the fish that did survive have now left the vlei.

The big issues that have been highlighted by many people at various levels on this issue are.

1. The vleis low capacity to handle contamination primarily due to extremely high levels of siltation. The situation is so bad near the mouth that on a springtide only 20-30cm of water can flow over the various sandbanks. Roughly 15-18 years ago a large dredging effort deepened the area between the road bridge and 150m North of the foot bridge. Two years later and the difference to the vlei in terms of fish numbers was remarkable as the salt water intrusion on a spring tide could be visually seen well into the main vlei.

2. A improvement to the rubble weir and sewerage pipe at the mouth that currently do not allow any decent volume of water to flow into the vlei. Perhaps the pipe could be re routed along the contour of the road bridge instead of directly across the vlei and the weir could be changed from a static system to one that can be lifted on springtides ( many more knowledgeable and intelligent can surely come up with even better ideas) ?

3. A serious problem with compliance and enforcement. Despite a dedicated response over the past week by various enforcement groups fish still were poached and when this problem was at it's worst hundreds of leervis, kob , steenbras and bull nosed mullet were massacred with pitch forks, spearguns and foul hooked. I am not sure if any of the dozens doing this were even fined? Can a telephone number be given to the public that can be called in future as various concerned people were verbally assaulted and they risked physical assault when they tried to save fish and stop poachers, activities that enforcement officers should have been doing.

As Dalton correctly pointed out the vlei is at a crossroads and if immediate action is not taken we will have no productive estuarine system in False Bay and indeed right up to the Breede river. The vleis' ability to act as a shelter/reproductive/feeding area for various important fish species was clearly highlighted by virtue of the massive volume of fish that tried to escape this latest contamination. In addition to this many bird species, otters, water mongoose and other forms of wildlife is dependant on fish in this system.

As one of many concerned members of the public I can understand that these issues cannot be rectified without substantial finances. It is therefore hoped that the people at senior management levels tasked with managing this area take this latest incident as a means to highlight the plight of the current situation at these relevant funding levels and concrete steps are taken to rectify the situation.

In this regard it would be appreciated that concerned members of the public are informed what the outcome of the upcoming Zandvlei meeting is in terms of a plan going forward.

Thanks to all who made an effort to help in various ways with this latest event.

Chris

**Flubber** · 10-04-12

For those who asked regarding Zandvlei...

A quick update (my 2C's) after a quick visit on Saturday.

As you all know the mouth has been opened last week which led to the outflow. The water on the yacht club side very discoloured, lots of foam and silt around, thus not very favourable for flyfishing. Water closer to the footbridge looked much cleaner better... A few leeries was spotted but no hookups as far as I could gather. Talked to a local who flyfishes there quite often, his take is that most of the big garrick have exited the estuary, a few small ones are still around. Lots of small baitfish (looked like herring?) also around. The guys used quite small flies...

The rain spoiled the fun somewhat, however it is very encouraging to see the conservation management patrolling the area... They were there early morning checking...

Regards

**BuzzLiteBeer** · 10-04-12

Please all take note of the environmental emergency standby number 083 499 1717 for future reference if you see any illegal activity at the vlei.

Originally Posted by Mike Taylor

Hi Garnet,

Is the Evironmental Emergency Number given by Cassandra Sheasby only for Zandvlei, Cape Town, or is it a general number for use anywhere? I'm thinking in particular of Hermanus where there've been two incidents that I've wanted to report (poaching and a sewage spill) and not known who to contact. Both the police and Overstrand Municipality are useless.

Originally Posted by BuzzLiteBeer

Hi Mike. I'm waiting on a reply from Cassandra.

Received this morning.....

This is the South Environmental Emergency and stand by number for the City of Cape Town Nature Reserves, so it covers Zandvlei, Rondevlei, Zeekoevlei, False Bay Ecology Park, Kenilworth, south Satellite sites, Strandfontein Birding Area and Muizenberg East.

**BuzzLiteBeer** · 11-04-12

Hello All

I would like to (try) add a bit of clarity to a couple of the issues raised by Chris Fallows in the order that they appear below. On a positive note, based on more than 10 years seasonal fish monitoring (a DAFF Fisheries Research / City collaboration), similar surveys from the early 1990s and some even earlier data, the current fish assemblage of the estuary is the healthiest ever recorded. Much of this can be attributed to existing mouth management that allows intrusion of saline water much further upstream than was the case throughout most of the 1990s. The reappearance of benthic feeders and dwellers such as gobies, pipefish and white steenbras as well as expansion of sandprawn beds indicate well oxygenated bottom water and that anoxic / hypoxic conditions don’t occur throughout the deeper parts of the system as did previously.

The recent event in which fish became concentrated in the lower reaches was most likely due to two separate events happening at the same time. Firstly, day / nighttime fluctuations in oxygen levels, supersaturated during the day, hypoxic at night have been happening over the last four weeks or so and are a natural product of plant (algae, pondweed etc ) photosynthesis and respiration. Low nighttime oxygen levels may be exacerbated by algal blooms that occasionally occur due to the estuary being within an urban catchment and eutrophic. Secondly, throughout the winter rainfall zones of SA, fish in rivers (eels) and estuaries take the first significant Autumnal pressure drop as a cue to begin moving towards the mouth as this usually indicates the onset of rains and time to be flushed out to sea. So, fish in Zandvlei began moving towards the mouth but had to contend with low nighttime oxygen levels as well as evidenced by surface-breathing and other strange behavior. Also, so many fish being concentrated in one spot would also have depleted oxygen in the water and most fish would already have been stressed by having to repeatedly cope with the low nighttime levels in the weeks previously.

1. The vleis low capacity to handle contamination primarily due to extremely high levels of siltation. The situation is so bad near the mouth that on a springtide only 20-30cm of water can flow over the various sandbanks. Roughly 15-18 years ago a large dredging effort deepened the area between the road bridge and 150m North of the foot bridge. Two years later and the difference to the vlei in terms of fish numbers was remarkable as the salt water intrusion on a spring tide could be visually seen well into the main vlei.

The estuary is not contaminated or toxic but is experiencing nighttime hypoxic conditions. The marine sediment (silt) at the mouth and resulting shallow water probably resulted in fewer fish succumbing to low oxygen levels (pity about the bad behavior of the public). The dredging that happened previously was almost on an annual basis and removed most of the sandprawn beds existing at that time. It also created deeper waters in the lower reaches that although saline, didn’t move anywhere, became stagnant and anoxic. Sandprawns also play a major role in estuaries by oxygenating the sediments and by controlling plants and algae by turning over sediments and smothering new plant growth. The actual process that occurs once dredging has been done is that the more saline and dense seawater flows in through the shallow canal and then underneath the more fresh less dense estuary water finally coming to a halt in the deeper dredged “hole” as it dams up against the shallows further upstream. This water and the sediment eventually becomes anoxic.

2. A improvement to the rubble weir and sewerage pipe at the mouth that currently do not allow any decent volume of water to flow into the vlei. Perhaps the pipe could be re routed along the contour of the road bridge instead of directly across the vlei and the weir could be changed from a static system to one that can be lifted on springtides ( many more knowledgeable and intelligent can surely come up with even better ideas) ?

Yes, removable of the weir would improve ecological conditions in the estuary but boating, sailing etc would not be easy for extended periods. The weir doesn’t allow maximum tidal exchange but it also means that, with the current mouth manipulation (the best that circumstance allows ), there is a nett import of marine sediment into the system. Removal of the weir would allow more scouring of these sediments but water levels would drop below the comfort levels of resident boaters. Ideally, from an ecological perspective, the weir should be removed and water levels allowed to rise against the berm to at least one metre above that currently permitted, for maximum scouring to happen. However, this would be well above the comfort levels of Marina residents. Finally, as correctly pointed out, innovation is needed and there are a number of ways to manipulate the estuary mouth ranging from constant excavation to inflatable weirs, most of them expensive.

"I'd take the awe of understanding over the awe of ignorance any day"

(Douglas Adams, The Salmon of Doubt)

Dr Stephen Lamberth
Inshore Resources Research
Branch Fisheries
Department Agriculture, Forestry & Fisheries
021 402 3159

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

"So long and thanks for all the fish"
(Douglas Adams, The Hitchhiker's Guide to the Galaxy)

BuzzLiteBeer
Flyguy
See attached images

Courtesy of Mark Stotesbury

**BuzzLiteBeer** · 11-04-12

Massacre roundup by G.Lawson.....

http://www.zandvleitrust.org.za/art-...ch%202012.html

http://www.zandvleitrust.org.za/art-...0-%20fish.html

http://www.zandvleitrust.org.za/art-...il%202012.html

**BuzzLiteBeer** · 13-04-12

http://youtu.be/n3Ir3uEEaOc

**BuzzLiteBeer** · 15-04-12

Fish are now dying in their thousands and more sewage spills have been reported. The mouth has now been closed by the City. NOBODY SEEMS INTERESTED IN REMEDYING THE SITUATION

==============================================
To all on this list in your respective capacities.

I suggest anyone who is concerned about Sandvlei go down to the mouth right now.

The situation that will greet you will be one of stinking, dirty oxygenated deficient water and hundreds if not thousands of dead and dying fish. These range from soles and eels to stumpnose, steenbras and small leervis not to mention thousands of estuarine herring and southern mullet. People have started stoning them and no doubt will eat them. Whether they are of eating quality who knows.

Scientists have pointed out that the water is currently not contaminated, , but anaerobicly depleted of oxygen.

Having just stood at the mouth along with many of the very angry people we would all like to know what is the game plan going forward as clearly the issue is serious. Whatever the problem we need a solution.

Cape Nature, City of Cape Town, Scientists , influential people on this list, many of whom sit on panels that make decisions pertaining to this vlei, what happens now?
We all know it should never have got to this stage, steps should have been taken long ago to avoid this as clearly there have been signs a long time coming, the vlei did not silt up overnight, sewerage did not suddenly run into the vlei unabated for 5 days and nitrates did not get to the levels they are at in a few weeks.

The sad reality is that Sandvlei is Cape Towns only viable estuarine system and arguably the most important one from here to the Breede River, this place really needs to be looked after.

Please at the very least let the people know that there is an action plan or that there is no action plan.

Please answer questions such as , can the vlei be built up from the base again, do the vleis sandbanks need to be dredged, do we need to replace the rubble weir, does the vlei need to be dredged of too many nutrients in the main vlei, is there adequate control of nutrients being fed into the system via the Keysers and Sand rivers?

Opening the mouth now may save a few thousand fish and would no doubt go some way to at least showing a commitment to removing the distressing scenes that are playing out at the mouth BUT it is the bigger picture that needs urgent action and communication.
Right now people believe nothing is being done to solve this problem due to no communication on the issue. It is no good arguing about it, rather those that are tasked with managing the vlei please give us all the game plan going forward as many people are concerned in various capacities.

Sincerely

Chris Fallows