Stella

Erm, exactly how is any of that an assumption? 'Whitebait' comprise of five species: Inanga: general decline Koaro: general decline Banded kokopu: general decline Giant kokopu: threatened Shortjaw kokopu: threatened There is PLENTY of scientific literature indicating that loss of habitat for both adults and juveniles, as well as loss of spawning habitat (which is different to adult and juvenile habitat), is a leading cause of the decline of each species. 'Habitat loss' includes effects from loss of riparian forest and low vegetation, sedimentation, dams and perched culverts preventing fish passage, and the definition is often extended to water quality degradation (which has a strong limiting effect on fish) due to land use changes and intensification, point-source pollution, fertiliser run-off etc etc etc Now, the effect of whitebaiting on the decline of these species is less quantifiable. However: The literature shows that whitebait do not really move under darkness, however the whitebaiting regulations limit people to only fishing during the day, when most of the whitebait run. They also mostly hug the banks, as that is where the flow is less allowing them to swim further. The regulations limit fishing to the edges of streams and rivers. Some whitebaiters will fish a site almost every day for a season. Also logically, removing large numbers of juveniles from a population of a threatened species, one that is already limited in every other way, is going to have a negative effect. As I say, very hard to quantify, but as 'assumptions' go, it is not a wild guess, there is an awful lot of research going into whitebait because of the decline. Habitat is by far the greatest factor, but the collective catch of many hundreds or thousands of juveniles per year will be having a negative effect. Based on several mark-and-recapture studies (they dye the whitebait!), between 1.5 and 44% of the whitebait were recaptured, with an average of 14% (ignoring the highest number, which was bit of an outlier). It is estimated that 20% of whitebait that escape the nets survive to adulthood. If more escaped the nets, maybe more would survive? It is a question that is extremely difficult at the moment to answer: is habitat loss or fishing the biggest bottleneck? And is what we are seeing now going to change dramatically over time? Agricultural land use intensification over the last 10 years is having a tremendous effect on our rivers. Will any of the whitebait that swam in today in your nearest river even be alive to spawn in 10 years time? Genetic research shows that there is very little movement of whitebait between rivers. It appears that the larvae loiter around the river mouth then head back in to their natal river. If the habitat of a catchment is significantly destroy for just one life stage, that is going to severely bottleneck the population, and now it turns out that that population will not be greatly augmented by healthy populations in neighbouring catchments. Yes, whitebaiting is legal and administered by DOC. To many that suggests that it must be sustainable (just like hoki, orange roughy et al :roll: ). However it is also a cultural fishery and could you imagine the uproar if it was restricted further? Personally I would like to see whitebaiting permitted for individual use, but ban the commercial sale of whitebait. The cultural tradition remains, but yet another Tragedy of the Commons is averted. Actually the vast majority of diseases and algae are present in your tank already. With whitebait there is certainly a high risk of introducing whitespot (which does *not* live in the water anyway) and that is about it.

Wrigglers, daphnia etc They are pretty tiny when they first come in, so restricted to tiny foods, but they EAT. If in a bare-bottomed tank, whiteworms are good. I say bare-bottomed because they don't have much inclination to graze and delve into stones for lost food. Bloodworms are not very good for raising fast-growing fish. They tend to just stunt. Although it is a useful food for small recent captives if you don't have anything live. Just be really careful to keep them in good quality water, and yes, whitespot is often an issue. They are going through MASSIVE physiological changes to be able to deal with freshwater again, so they are susceptible to things. (Note: whitebait and small galaxiids often come into captivity with what looks like whitespots embedded UNDER the skin, not protruding at all. These are completely different and quite benign parasites that will disappear after a few months)

Well, the population will, over time, because individuals showing the bright colour phenotypes will be more easily removed from the gene pool by predators. Individuals retain their own phenotype for life. While koi have been in Europe for a long time, long enough to show at least significant reversion, it is also likely that more recent releases would maintain higher levels of non-wild colour variants than you would expect otherwise. Anyway, DAMNED IMPRESSIVE FISH

You will probably notice a reduction in frequency after you do a water change, then it slowly builds again. I am guessing it is the same principle at work as is behind marine protein skimmers?

Apparently they taste really good! Are an especially good aquaculture option because they are vegetarian. If that is the plan I see nothing wrong in growing one up out of interest and then eating it because it can't be kept forever. Much the same as your average pet lamb.

Just out of random interest, are all Arowana in NZ the same species just different colour types, or are there different species?

Preacher, that would be cool! Though it is a single-species monoculture. I guess in the documents they were talking about the possibility of introducing other rare species. The only locally relevant ones I imagine would be brown mudfish and dwarf galaxias, neither of which would be visible. I guess other kokopu or smelt could work, but they would have to be taken from a landlocked population otherwise they wouldn't be able to breed. Non-diadromous bullies could work in the lake too. Making the water outlet navigable to juvenile fishies would likely also make it navigable to terrestrial pests. Would be terribly difficult to make that work without it getting clogged up constantly. Bit of a shame. My father's partner is a volunteer and leads night tours through the sanctuary. Sometimes they get kiwi kicking around their feet! Friends of mine said they were watching a large banded kokopu there once, lazing about in the sun. A staff member came over and asked what they were looking at. He had no idea about the fish! :roll:

Oops, ok this was a week ago, so you have probably seen if anything is going to happen or not. Even if irrelevant now for you, it might be useful for people trawling old threads. In general: If it is into the flesh, that is a bad thing. Otherwise tails usually grow back fine. If the water quality and maintenance is really regular, your chances of infection are low, because the fish should be healthy and the water clean. If you have been slack, be more paranoid and do more waterchanges, though don't do a huge overhaul. An infection is furry. A regrowing fin is a thin, fine membrane first and usually grows pretty fast. If an infection starts, add salt at a rate of 1/2 tsp salt per litre. Double the regularity of the waterchanges and replace the salt removed each time. As for your koura, how big is it? I find they become risky at 7cm and bigger, but a lot depends on the personality of the cray and the size of the fish. If it is little, just keep an eye on injury frequency. Crays are fast learners and he might have just learned that if he attacks fish he gets food.

Found this today, a really clear and concise document about what, why and how they are going to do it: http://www.doc.govt.nz/upload/documents ... t-2010.pdf Very interesting read, I HIGHLY recommend it. Looks like they are going to electrofish the streams and put the banded kokopu in the trout-free streams and in live cages/boxes. These are set in the stream so water flows through them but the fish can't escape. Multipass electrofishing will probably remove the majority of the kokopu. Now people may argue if the kokopu can be removed like that, why not use that to pull the trout out? Well the kokopu are most likely to be in the streams, while the trout will be in the lake. Can't thoroughly electrofish a lake like you can a small stream! Smaller trout will be in the streams, and conveniently they will probably need less poison to kill than big trout, as it is difficult getting an even mix through a stream. I fully accept that there will be some by-kill of kokopu, but just like with 1080 and possums, the trout are killing the kokopu anyway. Once the trout are gone, the kokopu will be able to increase, probably dramatically at the start as there will be more food available for juveniles.

So, if someone knows they are being brought in, it is therefore possible to know which store it is for? It does astonish me that these fish are in the aquarium trade.

Wow, dramatic photos! As an aside: Last summer I flooded my entire house (filling a tank with a hose, forgot, and went out - stupid!). Anyway, after it was all dry there was bit of a wet carpet smell. I sprinkled baking soda fairly liberally on the carpets and left it for 24 hours then vacuumed. No more smell! Baking soda is amazing multi-purpose stuff!

I would love to see them rotenone Karori. Rotenone is a plant-based toxin, another name for it is derris dust - you can buy it at the supermarket. It is used extensively overseas, especially in the US, and has been in commercial use for the last 150 years. It is used as a pre-harvest insecticide on food crops, and many other uses. It degrades fairly quickly, the rate depends on various things but usually a matter of days to months, and is considered to be 'environmentally benign'. It is used at very low rates (~1ppm) but dosage depends on species, turbidity of the water, and lake bottom complexity. It affects fishes' gills, blocking oxygen uptake and causing them to surface. Fish are then easily caught and if placed in fresh clean water most will have a full and fast recovery. It is preferable to catch the fish as they surface as an enormous rotting pile of fish is not going to help the lake ecosystem. It is an insecticide and can kill off aquatic invertebrates, but these usually recolonise incredibly quickly due to flying adults or drift from upstream, just as in the wild after a massive flood. The Karori lower reservoir is completely [hmm, swearing is objected to here... you get what I mean] by perch. It is pretty much a perch-only system. The little perch eat the zooplankton (daphnia etc), which releases the phytoplankton (green algae) from herbivory, which is why the lake is subject to really bad algal blooms, and has helped the cyano take over. Brendan Hicks et al from Waikato have been intensively fishing the lower reservoir for years, I think at least the last seven, and removed a huge weight of perch using both netting and an electrofishing boat. Of course larger fish are caught more easily, so this has resulted in a major size skew, with far more of the small zooplanktivorous fish now which is potentially compounding the phytoplankton problem. There is absolutely NO WAY the perch can ever be reasonably controlled or eradicated without the use of piscicides. Apparently in the upper reservoir and in the streams that lead into it there are still banded kokopu. Given how long ago the reservoirs were built, and how to outflows are constructed, it is highly unlikely that any of them have come from the sea, so they have managed to form a landlocked population. Get rid of the trout and the bandeds will be able to take over again - trout have a strong predation effect on galaxiids under 10-15cm. An amazing example of the use of rotenone in NZ is Lake Parkinson near Auckland. In the 1960s exotic weeds got in (please note: most problem aquatic weeds in NZ were released from aquaria) and rudd and perch or tench were released illegally. Within 10 years the lake was mostly weeds and the rudd had destroyed the put-and-take trout fishery. They put in grass carp to sort the plants in the early 1970s, and after 6 years all plants were gone, including those that could grow back from rootstock. They rotenoned the lake and removed all the fish - the grass carp and trout were revived in clean water. Over the next few years the native plants regrew naturally from the seed bank in the sediment (exotic plants do not have both sexes here yet, so no seeds from them). A very interesting report prepared for DOC by a Waikato native fish scientist: http://www.doc.govt.nz/upload/documents ... SFC211.pdf Also a paper on Lake Parkinson: http://www.doc.govt.nz/upload/documents ... /aqua5.pdf So far most of the comments have been very negative but with little actual content or reasoning. I would like to know exactly what people are objecting to so we can have some actual debate.

Wow, interesting that people have had luck with them breeding. I understand they are supposed to need salt water (maybe just estuarine). Can you please post more details of how it worked?

Sounds like it is a LONG way off being useful, and is aimed at the aquaculture market, but interesting. http://www.sciencedaily.com/releases/20 ... 162005.htm Progress on Vaccine for 'Ich,' Bane of Fish Farms and Home Aquarium Hobbyists ScienceDaily (Aug. 30, 2010) — Tests of the potential vaccine against "Ich" ― the dreaded "white-spot" disease that plagues fish in commercial fish farms, public aquariums, pet fish retail outlets, and home aquariums ― are raising hopes for finally controlling the disease, scientists reported at the 240th National Meeting of the American Chemical Society (ACS). "Outbreaks of the parasitic disease caused by Ichthyophthirius (Ich) can result in losses of 50-100 percent of fish," Dehai Xu, Ph.D., said in presenting the results. "The disease is very common, and almost every home fish hobbyist has encountered it. Once the parasite infects fish, and starts growing in the skin, fins, and gills, there is no really effective treatment. Ich causes losses estimated at $50 million annually. It would be much better to prevent the disease." As an indication of the difficulty in treating Ich outbreaks, Xu used the example of an infection that strikes a commercial fish farming pond, which might have a surface area equal to 10 or 20 high school football fields. The typical treatment involves pouring in a solution of formaldehyde, a potentially toxic substance. Hundreds of gallons might be needed, and farmers might have to repeat the treatment several times. Even after treatment, the fish would be at risk of reinfection if they encountered the parasite again, he said. "To vaccinate against Ich, you would need much less medication, and it would not pose an apparent threat to the environment," Xu pointed out. "And you would need just one treatment to make the fish immune for life." Xu explained that efforts to develop an Ich vaccine have focused on use of so-called "trophonts," which are the infective stage of the Ich parasite's life cycle. Trophonts burrow into a fish's skin, fins, and gills, causing the white skin spots characteristic of the disease. Those efforts have been hindered, however, by gaps in scientific knowledge about how fish develop protective immunity to trophonts. Xu and colleagues, Drs. Phillip Klesius and Craig Shoemaker, who are with the U. S. Department of Agriculture's Agricultural Research Service (ARS) in Auburn, Al., set out to fill those gaps. Their study evaluated influence of vaccine formulation and doses of vaccine on protective immunity of channel catfish against Ich. The results showed that vaccination with live Ich theronts and trophonts killed with high-frequency sound waves stimulated production of protective antibodies in the catfish. "This study demonstrated that vaccines against Ich induced protective immunity and could provide a unique solution to prevent this parasitic disease through vaccination," Xu said. "An Ich vaccine would have great impact by preventing the disease, minimizing loss of valuable fish and increasing profitability of aquaculture." Xu noted that the study was a small, laboratory-scale endeavor, with unsolved problems on the road ahead to a commercial vaccine. One, for instance, involves producing a large quantity of Ich antigen for the vaccine and then formulating a vaccine that can be easily administered to large numbers of fish in a "bath" or in food, rather than by injection. In the bath approach, fish would be kept in a container or an enclosure with water containing the vaccine. This study is within the component of ARS National Program 106-"Aquaculture" to improve health and welfare of aquatic animals. Xu and colleagues hope their study will bring more attention to the research to combat this disease. http://www.sciencedaily.com/releases/20 ... 162005.htm

Nope, me too Conjured up some great mental images.

Yep.

The snails in your filter may be a native also, Potamopyrgus antipodarum: http://en.wikipedia.org/wiki/Potamopyrgus_antipodarum Tiny little guys. I had huge population of them in one of my tanks but I NEVER saw them, except in the filter or when I used the gravel vac. I have printed out a handy guide at home for identifying snails, I will find it and post the link when I get home.

You said you were using a mature sponge filter. How was it matured? Possibly there was more bacteria in the sponge filter than was being fed by the tank processes. They could have died and added to the spike. You said you were feeding liquifry and green water. It is unlikely that they would be herbivorous. Not sure what is in the liquifry. In the wild they are zooplanktivorous. What did they feed them in the inanga paper? I imagine rotifers and similar. This may sound like a really stupid question but has to be asked... I assume you are using proper marine salt for making up water for marine tanks, not any other sort of salt or 'aquarium salt'? Can you try rainwater? Just thinking through the possibilities.

Gary probably mated with Gary (serious) Quite clever if you want to build a population quickly. Odd little flat round snail. If it was pale and like a limpet (no spiral) it was likely a ferrisia, very common in aquaria, most people don't know they have them.

I open my cannister filters once every six-12 months. They get the lightests of rinses. As Caryl says, the crud is doing the work. A really good idea is a putting filter foam over the inlet. This will catch most of the crud and can be washed out weekly. Reduces solid gunge going into the filter and clogging it. I had a soft sponge filter thingy over mine but it compressed down and slowed flow to the filter. It needs to be fairly sturdy.

I guess I have been doing it five years now. I used to have goldfish but now I couldn't contemplate anything non-native! Sigh, purist. I have had to cut back in the last year or two. Now just got a giant kokopu, two common bullies and three species of mudfish. While I mostly have rare ones now (more accidentally than design) bullies keep topping my list as the coolest aquarium fish. Also started a pond tank recently so I can watch pond critters doing their thing instead of being eaten. Truly fascinating and blissfully low-maintenance. What sort of kokopu do you have?

You betcha! :bounce: How long have you been into natives? Sounds like you have a nice addiction going there

They all do It is actually the exact same chemical as is in cucumbers. In your area it is Stokell's smelt most likely. Do a bit of searching, and particularly look in your library for NZ Freshwater Fishes: A Guide and Natural History (or similar) by R.M. McDowall They most definitely can be kept. Can live for three years if they survive the first few days (notoriously good at rolling over and dying if you look at them funny at the start). Cold water is essential. A LONG tank is good, and 5+ for lovely shoaling. A 4ft tank would be best. Would go well with some bullies in the bottom for action at different heights. I would also be careful with lids, they can probably jump out. Please keep us informed how you go! I haven't kept smelt yet myself, but they are a very pretty fish. And PHOTOS 8)

LOL love it!! :lol: And quite true.

The pH is unlikely to have much effect on most natives. The range that they are found in is tremendous. (Something like pH3-8 for giant kokopu!) With native pH testing is more of a curiosity than anything. What is FAR more important are the ammonia, nitrite and nitrate levels. Inanga can die in captivity from being egg-bound. It is the wrong time of year for that, and it should have a distended abdomen if that was the case. They have been known to live 3-5 years in captivity (one year in the wild, dying after spawning).