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Thread: Conservation- some notes and updates

  1. #11
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    Quote Originally Posted by clarias View Post
    Although if people were, rats and cockroaches would be too. But everything else would be better off
    I could'nt agree more.

    http://www.flytalk.co.za/forum/showt...2743#post72743
    So Long, and Thanks for All the Fish.

  2. #12
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    Just spoke to our lecturer, it is not known whether ALL leeries head up to Natal to spawn, as some big ones stick around down here. The sardine run definitely does play a role in their life cycle though.
    Apparently genetic studies are currently underway to determine whether there are separate populations in southern Africa.
    Also, leeries don't nessessarily need estuaries as nursery areas, they can grow up in sheltered bays too, which explains the west coast/ namibian/ angolan populations, although rivers like the Kunene are important.

    The other thing was that it is HIGHLY unlikely that leeries spawn in closed estuaries, no matter how big the system. Recruitment occurs during overtopping events.
    Grunter eggs were found in the closed St. Lucia system, but it is not known whether these would survive, as they also have a pelagic planktonic phase. The fish may just have spawned because they were trapped.

    My weekly update....
    Regards
    Carl

  3. #13
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    Here is a link to some research regarding the larval stages, including good pictures of what RREEAAALLLYYYY small leeries look like....

    http://www.fisheggsandlarvae.com/EIA1%20Carangidae.htm

    From the site:

    http://www.fisheggsandlarvae.com/

    Enjoy!!!!!

  4. #14
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    just a repeat:

    Chris you mention that you are worried where the money goes. I don't know, but with the recent distribution of the new regulation pamphlets, big upgrades at some of the marine institutes etc. it would seem that this money is being channeled in the right directions. I doubt whether the revenue of licences is very much, which may explain the lag.
    I'm also pleased to see how many MPAs (Marine Protected Areas) have been proclaimed. These are really effective, as they are way easier to police than catch limits etc.

    I believe they are trying to close some of the main kob estuaries to fishing- a big step in the right direction if you ask me. If only they'd close the Breede river at the time when the post- spawning broodstock comes in to replenish their reserves.
    The only problem is every tight- lines Tom, Dick and Herrie that goes there to kill their 'big kob of a lifetime'. Yeah right, I think you would need about 5 lifetimes now to catch that fish.
    That's a thought! I think I should try calculate that probability. Using the tag recapture statistics one could work out the number of adult kob around. Then
    divide this by the number of fishermen hoping to get their kob of a lifetime...
    I'm sure one could work this one out accurately. I have seen the tagging stats for some of our fishes, and what is immediately apparent is that almost all the kob tagged were caught again. This means either two things, that the fish hang around in one place and are easily caught (not the case in migratory kob) or that there are seriously few left...

    Anyway, I hope closed estuaries gives these fish the break they need at a time when they are most vulnerable....

  5. #15
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    just a repeat from another thread (where it was a little off topic). Also wish I could move this thread to 'Conservation General'- yellowfish don't do so well in estuaries...hang on, has anyone ever checked that in the Orange mouth??? Maybe there are seagoing LM!!!

    Gerrit, have a look at my album, I've added a pic of a bluegill...

    I personally have an extreme dislike of these fish. They are fun, and easy to catch on fly, and fight hard for their size (better than kurper!), look very pretty, are great to teach kids etc. etc. etc.

    These fish are often overlooked, I feel they may be doing more damage than the bass themselves. The adults feed on insects and small fish- which means they are in direct competition with,and predators on yellowfish and even bass!

    They quickly overpopulate a water. I disagree with Poppernel about bass loving them...these fish have evolved together with bass in the USA- and therefore have all the equipment and strategies to avoid being eaten by bass. They have some kind of mucus on their spines that is very painful if spiked by them. Bass do eat them, but I think given a choice between our soft indigenous fish and a bluegill- I know which I would choose!

    So ja, I rate they are more invasive and damaging than any of the bass. Why people thought that our own little vleikurper wasn't good enough I don't know...vleikurper are awesome, they just have nicer "personalities", they eat algae and don't compete with other fish, they certainly don't turn the tables and eat any bass! Plus they already occur here, so WHY, oh why did they bring us bluegill?

    This is off the topic I know, but I went to a very interesting talk the other day by a guy who'd done his PhD on the three WC big cyprinids (Clan, Witvis and Sawfin). Make that 4, there's also the Sandfish...wait, now i've confused myself and I don't have the book handy...
    Anyway, it was pretty interesting seeing exactly what's going on in those rivers and the combination of factors that have seen the decline of these species in the Olifants...basically a lot of it boiled down to us not really knowing enough about these species to understand what they need to survive...
    I think it would be terrible to lose these fish, I mean come on guys, the Clanwilliam yellowfish gets almost the size of the LM... and the others aren't that small either for the size streams they occur in. Certainly bigger than any of the trout people seem to haul out of those streams...

    My strategy with bluegill and sometimes bass is that if I catch them in a river where they are hammering natural fish, they get thrown on the bank for the birds or otters, or get cooked and eaten if they are big enough- which isn't very big, being a student and all y'know.
    I disagree with NC about the stance on dams though- I feel that seeing its an artificial environment, it might as well continue to support an artificial fish community (alien or otherwise, whatever occurs in the dam). Many of our indigenous fish don't do so well in dams anyway, so I don't see why the carp, bass and trout shouldn't be left there...

    Now back to studying,
    cheers

  6. #16
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    Always end up going off on a tangent and posting way too much, in all the wrong places... even my little thread here should rather be under general...anyway here it is again...some insect info!

    Oh ja, Dizzy, where did you find that Perlid? Surely not in the Vaal? I think they are quite strong indicators of river health.

    Its amazing what aquatic insects can tell us about the state of a river. We wrote an exam about it on monday. Just by looking at what families are present in a river, one can tell it's level of pollution, what type of pollution, the duration of the pollution, even the date and place where a spill occured. Unlike fish, these insects can't move a great deal to escape pollution spills, and, because their life cycle's are known, one can date events...
    pretty cool how insects can be used like that for environmental-, and even criminal forensics.
    There is a specific South African Scoring System (SASS) where one compares the different insect families in riffles. Each receives a score and from that you can get a rough indication of river health. The beauty is that you only need to identify to the family level, which can quickly be learnt by general assistants, allowing large stretches of rivers to be rapidly assessed and monitored.

    I saw some glossy reports on the states of various reaches of certain river catchments, detailing the current state and threats and impacts. Not sure where these are available and whether they are done for all rivers, perhaps some of you guys know? I think they were called 'the state of the rivers report' or something to that effect...

    Anyway, that's enough of an aside!

  7. #17
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    Just another addition to my little collection of loooong posts here...


    I'm not up to date with what's going on at the Jonkershoek and Hartebeespoort Hatcheries, but I'm sure there are other forumers in the know. Wasn't Harties at one stage spawning LMs? I'll also ask about Gariep, didn't know there was a hatchery there.

    The Lydenburg hatchery of the Mpumalanga conservation authority has been going through a lot of ups and downs, mostly downs, through the last years. Originally a MASSIVE trout facility that saw to all the state rivers and dams in the forestry areas and mountains being stocked...even the river that runs through the town was regularly stocked at one stage...back when you could purchase an angling licence for trout waters. Now they still do a bit of trout for job creation interests and such, but most of the dams are dry.

    In past years they did most of the yellowfish spawning work, trying to create hybrids in order to 'improve' them. Not sure where they stocked these hybrids, but they certainly caused a headache trying to identify any yellow that comes out of the local river! Luckily the new anti- translocation rule shows they've come a long way in terms of the conservation of genetic diversity...
    I think there are genetic studies being done on at least the vaal species, which should give interesting results...SAIAB (South African Institute for Aquatic Biodiversity) only recently got a fully kitted genetics lab, so watch this space for interesting new findings! http://www.saiab.ac.za/

    The artificial breeding of yellows seems to have been done, experimentally at least, for most species. The way it was done in Lydenburg was to have rocky areas at the inflow. Ripe fish would move to this part of the pond where they would be netted. (The fish shouldn't have a problem developing eggs at the right time of year and with the right feeding, but naturally spawning them would be difficult without the right natural conditions.).
    The fish would then be taken to the hatchery where the final stages of the gonad ripening would be stimulated with the injection of hormones (for more info on the hormones and processes related to this, you would have to be seriously interested in aquaculture- this would be a good start, even for anyone with an interest in aquaculture: the South African Aquaculture Association http://www.aasa-aqua.co.za/ .).
    Once the hormones have loosened the eggs and sperm, the eggs are gently stripped from the females (more like carp spawning than trout). Same for the male. I think a lot of the problems came with the fertilized eggs. In Lydenburg at least, trout trays (designed to simulate gravel beds) were used with some success. I'm sure further research (more interest needed, financial and economic) would vastly improve on this stage of the cycle. No idea how the young are raised, will find out this week though, where we'll be taking care of wild-caught SM and Moggel fingerlings for growth studies.

    I think there is a lot of scope for breeding yellows artificially, both for conservation and stocking into appropriate areas as angling fishes in dams. A lot more research is needed though into making this viable, and sadly a lot more funding, interest, incentive and some repairs to government frameworks are needed.

    For those REALLY interested (Scythe?)...here is a complete reference list from someones study (not sure who's, only the reference section came up in the search. Its from some work that UJ did, that university does quite a bit of aquaculture research up in Gauteng). Anyway, if you see any literature that interests you, type it into Google Scholar, and you should be able to access some of the original documents...

    http://ujdigispace.uj.ac.za:8080/dsp...%20Revised.pdf

    Incidentally, when do LM spawn naturally? Is it at the same time as the SM? I've been wondering what the impact, if any, of people in the rapids would have on their spawning. The SM don't seem to mind, but the fact that LM are so much larger and scarcer, makes me wonder whether they can handle the disturbance or whether they prefer a little privacy? This would be especially difficult if they spawn at a different time from the SM (when people generally stay off the spawning beds, I hope). What do you guys think? I wonder whether anybody has ever looked at whether an LM individual will spawn every year, or only every second year, or even 5?
    One never knows with large, long-lived species. They take quite long to build up the resources for spawning, but how long?

    Anyway, before I break the server...better be off to bed, off to work tomorrow to prepare for the baby yellows. Exams are over, YES!!!

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