Senin, 14 Juli 2008

Red Claw Information

Broodstock Crayfish from Cheraxpark are pond based not tank based animals.
The ponds are
• clay based
• well habitated with both hard and soft habitat
• supplementary aerated 24/7
• are only stocked with Redclaw – no fish NB we do not recommend running Redclaw with other livestock due to the very real possibility of cross contamination of parasites and diseases.
The water
• is plankton turbid -both phyto plankton and zoo plankton
• carry’s a dissolved oxygen reading of 8-12
• has a pH reading of around 7-8.5 with little movement through the day
• is dam water originally sourced from rain – not river water
• Nitrogenous wastes are dealt with adequately with Nitrosomonas and Nitrobacter bacteria naturally occurring in the clay bottom/walls

The crays are harvested and then graded in a commercial grader. Weighed and then put in the shower for 24 hours. The shower is run at 15 deg C which effectively allows the crays to in part clear their gastrointestinal tract and excrete ammonia whilst flushing their systems of clay particulate. This effectively assists in their taste if for the table but also assists in their intransit survival. The crays are then moved to the chiller for a few hours to effectively lower their core temperature down before packing for export. The chiller is run at 13.5 deg C in summer a little cooler in winter.

For export the crays are packed in airfreight approved poly boxes with a gel pack and layers of moist foam. They are individually examined and any crays with defects like tail blister are discarded. Only crays showing strong tail flick, the ability to hold their claws up and of export quality are packed. The crays are weighed on day of packing and an additional 5% is added to cover the odd death in transit.

The crays are driven to Brisbane (3 hours) in a covered vehicle and then vet inspected at AQIS before being lodged with the freight forwarder. Upon landing at Jakarta they have been out of water for around 26 hours, they will be cool but in a stressed state. Having been out of water for such a time their gills will be starting to dry- its important to get them back into water as soon as possible.

Handling / transport and stock losses

It should be noted that some stock losses will occur when ever you handle/transport and then restock animals in ponds or tanks – the losses can be from post harvest stress, partial gill drying, the onset of moulting or a combination of two or more of these things. But losses should be expected - generally if the shipment is handled properly in transit and the time out of water is reasonable, the DOA should be less than 5%(hence the additional 5% we give FOC(industry standard is 3% FOC stock) The majority of losses from the “stress of the trip” will occur within the first 3 days of restocking - the reason being that partial gill drying won’t kill the crayfish immediately but it will compromise the gas exchange that can occur ( both oxygen and ammonia)and effectively be responsible for their death within a few days . Generally speaking losses can be expected of up to 30% depending on the constraints of the facility they are going to and the subsequent water quality, the way in which they were handled in transit, the time of the year etc. Generally a loss of 20% or better is considered a good result depending on the total intransit time, the climate and the quality of the facility they are going to. Big Losses are an indication of either the shipment being in appropriately handled intransit (i.e. too hot – too cold) or something dramatically wrong with the facility they are being housed in - insufficient DO, elevated ammonia, contaminated water etc.

Large ponds
If you are acclimating into large ponds then salt bathing and the temperature adjustment we recommend for tanks and small volume ponds is not necessary. Caution though – when adding your crays to these large ponds – be aware in the warmer months that the water temperature in the shallows can be much warmer than in the deeper areas and we would advise that the crays are added to the deepest part of the pond. This may be achieved by gently tipping them in off a jetty over the deep water or perhaps even walking the boxes in to the deeper water and letting the stock go there.

Be vigilant with your water quality and be careful not to over stock or over feed your ponds. Overstocked ponds will have a negative effect on your growth rates. Over fed ponds will have a negative effect on your water quality which subsequently will have a negative effect on your crays and the ponds overall performance.

Small cement ponds and tank systems
If you are acclimating stock into tanks or small volume ponds then due to the smaller volume of water and therefore the usual warmer water temps, we recommend the following procedure involving the regulation of temperature. This prevents the crays from becoming temperature shocked coming from a cool box and going into water sometimes 10 degrees warmer Many variations of the temperature regulation method exist – we suggest you work within the constraints of your own facility and aim for the following principles
• Water temp .On arrival test the temperature of the crayfish in the box with a probe, then ensure the water they are about to go into is within. One and a half to two degrees of the internal box temperature. Use a chiller or ice / frozen bottles to bring the water temperature down to within one and a half to two degrees of the crayfish temperature and slowly let the water temperature rise so that the crayfish’s temperature can rise with its environment over a period of time.

• There has been variation with this water temp method depending on the sophistication of the facility – some have had increased success by holding their water temp down for a longer period of time and then increasing the water temp over the next few days Others who more accurately control water temps hold the crays for 24 hours at that cooler temp and then only raise the water temp by 2 degree increments over the coming days The method you adopt will largely be determined by the constraints of your facility.
• We recommend giving your crayfish a salt bath upon arrival providing your facility can cope with it.. This is not compulsory but if you choose to do this you will help to reduce the bacterial load built up during transport. Increase the salt level until you get to 5parts per thousand To achieve this level of dilution you use 5 kgs of salt for every 1000 litres of water. Keep them in this bath for at least 3hr.It should be noted that aeration in the salt bath should be vigorous and DO(dissolved oxygen )levels should be high.. A salt bath is stressful to the crayfish but it is documented that at 5ppt they will cope with these conditions providing oxygen is plentiful and other water variables are within suitable range. If your intransit time is extended due to your distance from the airport or the source of your crays then it might be wise to skip this and just get them into water as soon as you can.

Your other water variables are important:-
• pH should be between 6.5-9, preferably 7-8.

• Oxygen levels above 6ppm (mg/L), the higher the better within reason!

• Alkalinity and hardness levels greater then 50mg/l, but less then 400mg/l
• Ammonia and nitrite levels less then 1ppm, and preferably less then 0.1mg/l. You cannot achieve this unless your system has a biofilter on it. A Biofilter is essential on all tank and small pond systems. Ammonia and nitrite are highly toxic and can cause stress and subsequent death so constant monitoring of this variable is essential if holding your crayfish in tanks or small cement ponds
• Stocking density.- A good rule of thumb for stocking density is for every 10 kgs of crayfish you have 1000 litres of water . Use netting in your tanks to give them habitat and to allow them to use the entire water column. Over stocked tanks and ponds will lead to poor growth rates irrespective of quality genetics and good water quality.
• Light.- The crayfish you have purchased come from a pond environment – control the level of light your crays are exposed too – keep them in the dark for longer periods of time initially whilst they are settling in to their new environment.
• Initiate feeding as soon as possible after their salt treatment / or being added to their new homes.. This is important as the crays will not have eaten since the day before harvest and they will be hungry and be in need of quality nutrition. Be mindful not to allow uneaten food to decompose in the tank/ small pond as you will lower DO and compromise your water quality
• Timing –it’s essential that crays are back into water as soon as possible. If your facility does not allow you to get ALL the crays back into water upon their arrival then you need to do one of two things 1. Order less crays or 2.increase the size of your facility so that you can accommodate all the animals at once. Its better to skip the acclimation methods of salt bathing and temp regulation and get them into water then waste hours acclimating half of your shipment leaving the other half in boxes which are fast increasing in temperature
• Be realistic – you are getting crays which have been harvested, purged, chilled, packed and transported out of water for over 24 hours. They are arriving into a brand new environment, different water, different types of food – all these changes cause stress in the animal. Essentially you need to provide the best possible environment for those crays to settle into so they can overcome the stress of the trip.
• Stress and acclimation If restocked properly the stress related to transport should quickly subside as the cause of the stress is removed and crayfish will acclimatise quickly however if crays are continuing to develop tail blister (a visual sign of stress- not a disease) after 3 days of arrival then check your water quality because there will be another new cause of stress responsible for the tail blister. Ammonia and nitrite levels, dissolved oxygen levels, pH, overcrowding etc – these should all be re-examined until you can find and remove the new source of stress.
• In summary there have been many variations of the acclimation theme – however generally the key is to get them back into water as soon as possible and do your best to offer an environment as similar to the one they have come from given the constraints of your own facility.
(http://www.budidayalobsterairtawar.com)

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