Diary of a carp farmer

n my last diary piece I outlined the procedure that we go through each year to spawn our fish at VS Fisheries. Additionally I explained how the eggs are treated once fertilised and finally described how the fry are counted. In this month’s piece I want to explain how the fry are reared indoors before being stocked out. I also want to look at how we feed the stock around the farm and lastly I want to finish the series with an insight into one of the most important routine jobs throughout the summer: the management of water quality in the ponds.

As I briefly outlined last month, once the fry have been counted they are placed in large heavy-duty plastic trugs where they are reared for approximately ten-days. For a tiny carp there is just one extremely basic rule in life: eat or be eaten! It is a simple motto but their lives depend upon it. Basically the bigger a carp becomes the less chance there is that it is going to be snaffled up by a passing duck, savaged by a hungry water beetle or swallowed whole by a predatory fish. Effectively they need to eat their way out of trouble and this is deeply engrained within their instinct to survive. In the UK, predatory birds like the cormorant will take on carp of about 4lbs so young carp cannot really afford to stop eating until they have reached that weight. Unfortunately as I have outlined previously, most of them don’t win the race against the predators and in most fisheries they are eaten within their first few days of life.

Of course within the safe environment of the hatchery there are no predators at all. However, the tiny carp are not aware of this and set about their life’s motto with great gusto! The hatchery is warm at this point and consequently the fry are ferociously hungry all of the time. Regular food is therefore essential to fuel their rapid growth and to give them a great start in life. Correct feeding is absolutely vital at this stage and because the fry are within the safety of the sterile hatchery there is no natural food available. The fish farmer must now take on the task of Master Chef!

During this period the fry are fed on a diet of tiny, newly hatched marine plankton called artemia. To ensure a continuous high quality supply of plankton the artemia is hatched from dehydrated cysts (eggs). These cysts are miniscule and have the consistency of fine sand; to put their size into some context, there are about a quarter of a million cysts in every gram! The dehydrated cysts are re-hydrated and then hatched in several large conical-shaped vessels full of warm salt water within the hatchery. Amazingly within the warm water of their hatching cones this process is complete in under twenty-four hours and results in millions of bite-sized carp snacks full of nutritional goodness!

Once hatched, the nutritious artemia are introduced to the trugs of fry several times each day to make sure that the greedy miniature carp don’t go hungry. Although of marine origin, the artemia remain alive and active in the rearing trugs for a long period stimulating the aggressive little fry to feed. Effectively at this stage we are farming marine plankton which in turn allows us to grow our carp! Initially each feed is small because the carp are so tiny, however, over the course of a week their ration increases rapidly as the fish convert the nutritious plankton into growth with staggering efficiency. Within a week or so each tiny carp will have eaten its way through several thousand artemia. That equates to approximately 15 million artemia per trug in a week!

Of course, this conveyor belt of highly nutritious grub going into the rearing trugs and then through the fry’s gut ultimately produces waste products that require management. The water quality in the rearing trugs is carefully checked and regular water changes ensure that the fry are kept in near perfect conditions throughout their time in the hatchery. This is labour intensive work and requires patience and attention to detail. However, the reward for the long hours within the hatchery is to observe carp growing at a phenomenal rate. With every passing day they grow stronger, swim faster and become increasingly robust. After many years of fry feeding I still get excited as I witness many thousands of tiny near transparent fry rapidly develop into small fish. Of course this rapid change in size is giving the young carp the best possible start in life and it also tremendously increases their chances of survival once they are released into the fry ponds.

Usually within two weeks the fry have reached a stage where they are ready to leave the safety and warmth of the hatchery and be stocked into the fry ponds that I wrote about in the “Penners” issue of CARPology a couple of months ago. Although the hatchery is safe and warm, the very best place for the fry to grow and develop is in the natural environment within a rearing pond, eating natural food and grubbing about in the sediment. If I have done my work correctly then this stage in the fry’s development should be perfectly timed with a huge natural food explosion in the fry ponds. The fry ponds should be brimming with slow swimming daphnia and the fry are now just about big enough to tackle them.

On the first Sunday in June this year, just eight days after they had hatched, I carefully bagged up all of the batches of fry within the hatchery and over the course of several hours released them around the farm into the various fry rearing ponds that we use. As I released each batch I marked them off on my pad, recording the number and the parentage of the fry for further note.

Initially the young fish will harvest the natural food within the fry rearing ponds, which as I have already mentioned is the best quality grub they can have at this stage in their development. However, despite the ability of the daphnia to reproduce at a frantic rate, the young carp eat them faster than they can reproduce. It usually only takes the fry a couple of weeks to completely devastate the natural food within the pond and as they steadily clear the pond we gradually begin to introduce artificial food to replace the missing grub and therefore maintain the carp’s rapid growth.

The fry are fed using clockwork belt feeders which are loaded every morning with fine highly nutritious crumb food. The dust-like grub is sprinkled along on a flexible belt that slowly creeps along and rewinds itself onto a spindle. As the belt creeps towards the spindle, food drops off the belt into the pond below. Once reset and loaded, with food the clockwork feeders tick away during the day and gradually over a period of twelve-hours the day’s ration is dropped into the pond.

It normally takes the fry a few days to learn that the plastic box hanging over their pond is actually the carpy equivalent of a fast food restaurant. Initially there is no sign of the young carp under the feeders, however, as the natural food supply within the pond starts to disappear they steadily congregate around the feeder each morning. Within a couple of weeks the water beneath the belt feeders boils up and writhes with frantic fish each morning as they anticipate their food. They become more like thirsty festival-goers desperately bustling at a crowded bar than cautious carp waiting to feed. It is always great to see their enthusiasm for food at this point in their development. This busy feeding activity also allows me to see how they are growing and to adjust their ration.

If the water quality within the fry ponds remains perfect throughout their first growing season and the weather has been reasonably warm, then it is possible for carp in their first year of growth within the UK to achieve a length of about 15cm. It is important to say here that stocking rate, food availability and disease will all play a hugely significant role in their progress and should things be less than perfect then their growth will be significantly reduced.

At the time of writing this piece for CARPology (early September), the fry that I released in June have had a really good growing season. The best of them now look like proper little chunks; they have clearly lived their motto to the full. Those that I have managed to catch beneath the feeders now stretch across my open hand. They are perfect little characters that look set to become real monsters of the future. It is an unbelievable transformation in only three-months!

The correct feeding

Of course it is not only small carp that we are feeding throughout the summer. The second, third, fourth, fifth and sixth summer fish also require feeding throughout the warmer months. There is always natural food within all of our rearing ponds at the farm and we actually try our best to encourage its production, however, if we are going to achieve relatively steady predictable growth rates throughout the summer season, the fish require additional food.

At VS Fisheries we feed a mixture of different diets to our stock depending upon their age, the time of the year and the water temperature. In most cases we feed pelleted diets which are supplied from large fish feed manufacturers like Coppens and Skretting. These large international companies supply diets right across the world to a vast number of fish farming operations rearing a wide variety of different species. Therefore they are specialists at producing first class diets which are tailored to suit the needs of individual fish species. Additionally their products have a good shelf-life (normally six-months from manufacture) and therefore can safely be purchased in bulk. Both Coppens and Skretting produce carp and coarse fish diets that we have used in the last few years to feed our stock.

Pelleted fish diets like these are of course incredibly convenient and simple to feed to the stock at the farm. They are easy to feed with a scoop; they sink quickly to the bed of the pond and hopefully stay as an intact pellet for several hours allowing the fish plenty of time to find them. It is important to note here that the rapid breakdown pellets that are so popular within the carp angling world are not a great deal of use to us because they are difficult for the fish to actually eat once they have broken down to mush on the bed of the pond. We match pellet size to fish size as closely as is possible; the smallest carp receiving the smallest pellets, while the older fish are routinely fed 6mm pellets. In addition to the pelleted diets that are fed across the farm most days throughout the summer we also feed some soaked wheat to our stock on a regular basis.

I am often asked, “How much should I feed my fish?” whether they are in a garden pond, a fishery or a carp stock pond. My reply is normally something like this: it is reasonably hard to kill a fish through underfeeding; however, it is incredibly easy to kill a fish through overfeeding! Carp may not grow a great deal if they are only fed a little, but they will remain healthy and long lived provided they have sufficient nutrients to keep themselves ticking over. However, carp that are overfed are a great risk from all sorts of water quality problems and health issues. Too much food may be fine for a day or two but regular overfeeding will quickly lead to a dramatic deterioration the quality of the water and this can cause oxygen crashes where fish suffocate or other issues with toxicity which I will talk more of in a bit. As carp farmers we are trying to balance growth with survival; if we become greedy we risk losing the whole lot. I would always rather harvest a small carp than a dead one!

Feeding the stock at the farm is one of the most pleasurable jobs. I love pulling up in the fish farm truck at one of the feeding spots on a warm sunny mid-summer morning to be met with subtle clouds of murky water gently rising from the shadowy depths as the hungry carp grub about in anticipation of their next meal. A few moments later, as a scoop of pellets hits the surface, the activity beneath the water becomes intensified to a frantic barging as the fish compete for the food as it sinks. Another second or two and fresh columns of heavily silt laden water are thrust towards the surface by active fins, marking the spot where the pellets entered the pond perfectly…. breakfast is served! Watching these silty plumes rising from the spot you have just fed is a fantastic indicator that the fish are happy.

Monitoring water quality

One of the more mundane but hugely important tasks that is done every week around the whole farm is the monitoring of water quality. Unlike the oxygen content of air, the oxygen content of the water in lakes and ponds fluctuates a great deal and at times these fluctuations can be rapid and erratic. Because of this it is vital that we regularly test the level of dissolved oxygen in the water to ensure that there is sufficient for the fish stock to be healthy. Should any readings indicate a problem, then aeration needs to be increased to insure that the fish are kept comfortable and out of danger.

Another parameter that we regularly test is the ammonia content of the water. Ammonia is the most toxic nitrogenous compound and it is produced by fish as they breakdown protein to generate energy. It is then excreted through their gills into the water around them. Carp are really hardy, robust fish which can withstand a degree of pollution within their home, however, if levels of ammonia rise too high within their rearing ponds they can suffer an unpleasant end. The ammonia in the water is highly irritating to their gills and this leads the fish to eventually suffocate very slowly as their gill function slowly fails.

Ammonia is a tricky customer because it is not consistently toxic to fish. In fact, the degree of toxicity is determined by the pH and temperature of the water. Ammonia is more toxic in warm water and it is also increasingly toxic as pH rises. Therefore ammonia could be mildly toxic in a shallow lake at dawn and by late afternoon with the sun high in the sky it could become a mass murderer! With this in mind we keep close tabs on how ammonia levels are in our growing ponds and adjust aeration and feed rations as required to keep this unpleasant customer at arm’s reach.

Unlike the oxygen content of air, the oxygen content of the water in lakes and ponds fluctuates a great deal

Feeding the stock at the farm is one of the most pleasurable jobs

For me that makes farming carp in this country very special: we have the chance to see them grow really large

Tomorrow's dreams!

Well that just about brings me to the end of this series. I hope that you have enjoyed reading it and that it has given you all a bit of an insight into the way that carp are reared in this country. What we do is nothing particularly new; the Chinese were writing manuscripts about carp culture more than two thousand years ago and if I am honest not a great deal has probably changed! Make a hole that retains water, fill it with small fish, add some feed and then finally harvest the fish once they have grown – simple!

There are approximately four-million tons of carp farmed annually around the world and the vast majority of that huge weight goes directly into the human food chain. That is one difference with the carp that we farm in the UK; most of them end up going into fishing lakes. For me that makes farming carp in this country very special; we have the chance to see them grow really large and into old characters. As a carp farmer I love nothing more than hearing how someone has caught a huge fish that was once a tiny fry that I carefully looked after…. deep satisfaction!