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A Scientists Perspective on Esruary Life

Ron West - Associate Professor, Wollongong University

I was asked originally, to give a scientific perspective on Port Hacking, but I notice that the conference has expanded a little to include urban estuaries and so I thought I’d mention a few other places as well. But it’s very difficult to give a scientific perspective I guess so I’m going to add a little bit more than just a scientific perspective, I’m going to add a little bit of personal perspective as well. Basically I’m going to talk a little bit about what’s there and I thank Dennis for introducing us to some of the aspects that I’m going to talk about as well. I’ll mention something about what’s there, something about the present condition of some of those habitats particularly in Port Hacking and about other areas as well. I’ll also mention something about “what future do we actually want for areas like Port Hacking and other urban estuaries around the Sydney region?”, and then I might talk about a scientific perspective on management priorities rather than maybe a manager’s perspective.

So what is actually out in these habitats? In these estuary habitats there’s very diverse flora and fauna. We’re very lucky in the Sydney region that a lot of that flora and fauna persists and we still have very good diversity. If you were going to go out as a scientist and try and put them into categories, we’ve got some rough categories that we could use such as flora and fauna. We might then divide that up into saltmarshes, which is a part of the plant community that occurs right up the top end of the tidal area, to mangrove areas; and seagrass areas. And I’ll speak very briefly about some of the diversity of those groups and also about the fauna as well.

As Dennis said, Port Hacking is in pretty good condition in lots of areas, although I think we’re going to find out perhaps it’s changed in the last 50 or 60 years. Certainly if we’re going to look at saltmarshes, one of the main saltmarshes in Port Hacking area is around the Cabbage Tree Basin area. That saltmarsh is actually interesting because it was investigated right back in the 1900s in terms of the species that were there, and the actual area of saltmarsh. There’s some pictures and very interesting facts about the saltmarsh taken right back in the 1900s.

Well the saltmarsh are the plant communities at the highest tide. There’s lots of species in them and it is a plant ‘community’. The definition of a saltmarsh is basically: ‘a community that occurs in that upper area of tidal region that survives in saltwater conditions, often in very high salt environments in the soil’. There are about 40 species of plants in this region. The unfortunate thing for saltmarsh is that a lot of them are in private ownership, because of course, land ownership goes down to mid high water mark for the most part. And so a lot of the saltmarsh areas are actually in private ownership because they are up in the higher area of the tidal range. And for that reason, and because people like to fill these areas, they are certainly one of the most threatened communities in the Sydney region. So we’ve lost a lot of saltmarsh in the Sydney region.

The second community is the mangrove communities. We don’t have huge areas of mangroves in Port Hacking, but we’ve certainly got some good ones in the Cabbage Tree Basin area again as well as further down near Grays Point. And as a lot of us know, there are two species of mangroves: Avicennia, which is the grey mangrove, and the river mangrove (aegiceras). We only have two species in this area. More species are found as you go north, less species as you go south. They’re really a tropical plant, but these ones are actually adapted to this area. They occur in a number of locations. and are important habitat for a lot of bird life and aquatic fauna. For fisheries, the creek areas with mangroves are very important. We used to think that these were also under a lot of threat, but in actual fact they’re holding their own. In many areas, the problem with mangrove areas really is that we’ve changed areas of creeks. The actual area of mangrove hasn’t changed very much, but we’ve actually changed the type of mangroves, from creek habitats, into some of the other sorts of mangroves that people see taking over islands and things like that.

The other important community I always like to talk about is seagrasses. Seagrass is an underwater plant which flowers underwater. It is a very important habitat for a lot of fish life, for invertebrates, for crabs, and for a whole range of prawns. Basically there are three species of seagrass. The one of greatest concern is posidonia, which is a very slow growing plant and it certainly occurs out in Port Hacking. We have very significant areas in the Sydney region, particularly in Brisbane Waters, Pittwater, and Botany Bay which has extensive areas of seagrasses which have changed quite a lot over the last 50 years. Port Hacking also has extensive areas which have also changed quite dramatically over the last 50 years and, as I said, they are very important for fish and invertebrates. We’re actually using videos to look at fish communities as Dennis was talking about, but we’re doing it in fixed locations. The three species of seagrass are posidonia which I said was a very slow growing species, zostera and halophila. They are very important for fish communities.

Then we’ve got the algal communities. Algae are different from seagrasses in that seagrasses actually produce a flower and so they are a ‘higher’ plant. Algae on the other hand are ‘lower’ plants, and similar to ferns in that they don’t produce flowers. There’s very little information available really about algal communities in NSW generally and certainly specifically about each location.. Management has not been a priority for algal communities. There’s very little activity in preserving algal biodiversity in any particular areas.

The current issues that have come to the fore recently, as Dennis has mentioned, include caulerpa taxifolia which is beginning to take over quite large areas. The interesting thing about that plant, is that it’s very invasive. Even if you break it, the little pieces will begin to grow. If you go through it with a boat for example, every one of those little pieces that you cut up will grow into another plant. So it’s quite different from a lot of other plant communities.

The interesting thing about the algae is the existence of an extinct species we know about in Sydney Harbour. It’s the only known extinct algae in the world. One of the reasons we know about that is that because it’s a very pretty algae and in the 1800s people collected it and pressed it and sent it around the world as an example of the sorts of algae that were in Sydney Harbour. Unfortunately it can’t be found anymore. It’s the only known one that’s extinct.

The invertebrate group is a huge group of animals and one of the largest groups of fauna. And again, we really don’t know a lot about their distribution and abundance. We know little bits and pieces, but no detailed information in terms of biodiversity of particular sites. The knowledge is increasing, but we don’t have huge amounts of information. The invertebrate group range right from the seashore with various molluscs, crabs and so on, right through the system. Prominent examples are what we call nippers, or the bait that people collect. We’ve got a pretty large project going on with one of the PhD students at Wollongong University looking at these nipper areas the abundance of them, and their growth rates. So that will be quite useful in the future for management of these sorts of areas. It’s one of the few species used as bait from the wildlife in large quantities and so its quite an interesting study to find out what’s going on in terms of the populations there.

And then of course there’s the fish.. I think most people look at fish as a group and something I always like to stress is that we can look at them as a group but we need to recognise that they’re all individual species. Every fish species has an individual life history and life cycle and various requirements. And so looking at them as a group and saying “Fish are doing this, or fish are doing that” is not really the right approach to take. A lot of fish have very different sorts of requirements. I stressed the importance of seagrass beds earlier, and a great deal of fish live in seagrass beds, but there’s a whole range of fish that don’t. So it’s a matter of balancing some of these issues. Estuaries are well known as a nursery area for juveniles of many of our commercially and recreationally caught fish. In other words, we get very small juveniles into estuaries. For example, species of bream, all occur as juveniles, blackfish, garfish and I think if I ask the audience to name a few fish, you’d probably come up with about 10 or 12 species.. But if we look at the estuaries as a whole, and at the biodiversity, there’s actually several hundred species of fish in the estuary. Dennis mentioned the species called goby. There’s five or six goby species. There’s 3 or 4 garfish species. There’s 3 or 4 flathead species that occur in parts of the estuary. There’s 2 bream species: a black bream and yellow fin bream. So there’s a range of species, and a lot more diversity than people generally think about. Just as an example, there’s a number of leatherjacket species – we catch 7 species of leatherjackets just in the seagrass beds. And there’s a lot more species of leatherjackets within Port Hacking.

So what are some of the impacts and I’ll just mention a few before I get on to what I think are some of management priorities. Firstly, loss of wetlands. There are lots of different ways we are losing wetlands. One of them is boats and boat anchors. Certainly this is one example of how you might lose areas. Where boat chains are working around the seagrass bed, every single one of those boats in this photo has a hole underneath it. Every old mooring has a hole underneath it and none of those areas of seagrasses are regrowing. Now that’s particularly important in an area of posidonia which is a very slow growing seagrass. They just don’t come back in our lifetime. Jibbon I think is an example of where that’s happening in Port Hacking. But the other community is the saltmarsh which is also under some threat. If you examine a time frame taken locally in Cabbage Tree Basin, you can clearly see that in the 1950s, there was a lot of seagrass there. But in the 1990s its basically all sand and been replaced. So loss of wetlands, loss of communities is very important.

The second issue is loss of water. What do I mean by loss of water? Well we’ve cut off access to areas through measures such as flood mitigation gates of which many examples can be seen on the north coast of NSW, locally and certainly on the south coast. There aren’t as many around the Sydney area. Around the Sydney area, there’re certainly examples of the ‘weir’. Local examples can be found at Waterfall and at Audley. Those weirs stop fish moving up and down the river system. Quite a lot of the species of fish in NSW need to move up and down river systems in order to breed. Weirs stop fish breeding and stop access to quite significant areas. There’s been a longstanding proposal to construct a fishway at Audley. In NSW we have a program of putting in fishways or fish ladders into all these areas to try and get the fish to move through them. The fishway at Audley has been proposed for about, I think at least a decade. And the sign’s actually been sitting there for about 9 years, possibly 8, and nothing has yet happened. I don’t know what the situation is, but that weir needs to be fixed. And the reason it’s been a priority is because the fish communities need to get up and down that river.

So I’ve spoken about impacts on wetlands, loss of wetlands, loss of water etc. But the final issue is just basically: the issue of overfishing in terms of fish communities in particular – too many fishers and too few fish. Basically there’s really a fundamental misconception I think, in that most people believe that the reason why they’re not catching fish is because of commercial fishermen. Now that might be true, but the problem with the fish communities is that they are in a lot of cases, either fully exploited, or in some cases over-exploited. There are too many fish being caught. Whether they’re being caught by commercial fishermen of recreational fishermen is not really the issue. The issue is that there are too many fish being caught generally. Surveys reveals that there are actually more fish caught by recreational anglers. In most estuaries, there are more bream, for example, caught by recreational anglers and more whiting caught by recreational anglers. So I think that the fundamental problem is that we’re not accepting that recreational anglers also have an impact on fish.

Finally just a few thoughts about management. Management is about having a vision about where you want to go. We have some beautiful estuaries in Australia. Where do we want to head with them? I’ve recently been in the Philippines and I can tell you that some of the estuaries and some of the bays there are in very poor condition. We don’t want to end up in that sort of position here. We have a balancing act to play. In terms of management priorities, in terms of a natural resource, there are really three things that we need to concentrate on in managing a natural resource. One is that some of the resource has to be put away. And the way we do that is to create a comprehensive and representative selection of those communities. The second thing is that sustainable management has to happen with the rest of the resource, with that part that we’re going to go out and use. And the third thing is that we have to give special consideration to threatened species. So there’s three fundamental things there about managing a natural resource.

The one I want to just concentrate on is the one about total protection. The NSW Government has a policy of establishing an adequate and comprehensive representative system of reserves in the marine area as part of the government’s coastal policy. And the major action in that policy is to create an adequate and comprehensive representative marine and estuary reserve system. Firstly. What is best practice? How do we go about creating a comprehensive and representative reserve system? Best practice around the world says that we should put aside somewhere between 10-15% and maybe even up to 20% of those areas. As a guide, in Australia in relation to forests, we’ve decided to put aside 15% of the pre-1750 distribution of each forest type. That’s the Commonwealth policy in terms of forestry or that’s certainly the aim of the forest policy. What have we done locally in terms of marine areas? Well let’s just quickly go through each of our urban estuaries and see how much we’ve put aside.

In Brisbane Waters we have 2700 hectares of water area and the area that is put aside as areas that cannot be fished in and are marine reserves is zero. In the Hawkesbury River: zero. In Pittwater virtually none. In Port Jackson/Parramatta River: zero. In Botany Bay/Georges River we have 2 hectares set aside, which consists of that small area in the back of Quibray Bay which to which there is very poor access. Port Hacking, as we’ve heard, has an area set aside. It’s about 2 hectares of the 1130 hectares of water area in the Port. As a total situation, the amount that we’ve put aside is now 0.015% in the urban estuaries. We need to do something about that. There’s about a thousand-fold increase needed just to get us up to best practice. So of the 26,000 hectares of water area in the urban estuaries, we have 4 hectares set aside. Then we also have some reserves where we have the following rules: (1) A person must not wilfully disturb or interfere with fish in the reserve. The next rule is (2) you may fish with a hook and line. I’m not sure how else you can go out and wilfully hurt the fish, maybe with a spear gun, but certainly hook and line does as much damage as anything else. So I don’t really consider that to be a ‘reserve’.

So just very quickly in terms of final points. For Port Hacking from a scientists perspective, there are a couple of important things. The culling of the deer which is an issue for terrestrial communities – for the fauna and flora of the Royal National Park for example – will actually have quite an impact on the aquatic communities as well. The deer do tremendous damage to saltmarshes around the area. They actually walk across those areas destroying quite large areas of saltmarshes. So culling the deer will actually be of benefit to saltmarsh areas The construction of a fishway for the fish communities in Port Hacking is essential. I know the sign’s up there, but let’s actually do it! The other thing I’d like to suggest is that in terms of creating reserves, we need to think about where we can actually create those reserves in places like Port Hacking. My suggestion would be somewhere like Cabbage Tree Basin which has a very good range of communities and is already surrounded by National Park. But that’s only my suggestion and that’s open to community debate. I think it’s something we have to talk about though. And finally the major priority for all the urban estuaries is that I think that we should be looking to create a system of marine and estuarine reserves that meet the definition of protected areas and are comprehensive, adequate and representative and that is the government policy, so thank you.
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