Predation

Cormorant roost
Inland Cormorants.

Written 15th January 2011

The past twenty years have seen a dramatic rise in the inland Cormorant population and a corresponding rise in the adverse impact on fisheries and livelihoods. The mention of Cormorants in the angling world brings people out in a rash, they change colour and spit, splutter and dribble at the very thought of our piscivorous visitors. The frustration on the part of the anglers can be understood as they see yet one more nail in the lid of their fisheries coffin. The reason behind the increase of inland Cormorants can be attributed in the main to three factors.

Obviously the change in the birds status under the Countryside and Wildlife legislation that removed the bird from the quarry list , where it had a bounty on its head or beak to be precise, giving it protection under the law. Times gone by when netsmen paid their netting licence with the income from the Cormorant bounty are most definitely a thing of the past.

This period of change has coincided with the huge increase in disused gravel pits that have been flooded after the aggregates, clay etcetera have been removed. The after-use of these pits has for the most part hugely benefited society in providing areas for waste disposal, energy generation, relaxation and recreation. They have also provided many areas to the benefit of wildlife and the natural environment. It is this second area that I believe to be cynically exploited by many of the huge industries involved as they abandon pits under the guise of wetland habitats saving millions on restoration and after-use commitments; all too often leaving an alien landscape populated by alien species.

This increase in water bodies from the aggregate industry has coincided with the increase demand for potable water and the demands of the population making for the construction of new reservoirs across the land. Quite rightly these water bodies have been managed to maximise their benefit to society and wildlife and for the most part the balance is well met. In both instances there have been increasing frequencies, due to the financially difficult times we are in, for many of these waters to be managed to maximise their financial income stream. The result is we are seeing reserves and wetland sites becoming theme parks to drag in the public rather than a link with the local flora and fauna they are becoming stark islands of alien habitats and species.

In an effort to attract more birds, mammals and plants to bring in the every curious Joe Public we see every effort to encourage marine species to move inland; Tern rafts, artificial island for gulls and Cormorants, shingle beaches for Plovers and the list goes on and on. If you add to these the list of alien plants that have originated and find shelter in these pits many are now a far greater threat to the local environment than an enhancement. We will not see the aggregate industry rushing forward to correct any of these imbalances; they operate in the private sector and exist to make money. To abandon a pit under the wetland habitat banner is good news, itís a get out of jail free card, green wash is easier than expensive restoration. It is the planners in the minerals and waste departments of your county councils that need to be made aware of all the implications of this apparent bonus for flora and fauna. Itís no good prior to giving planning demanding every kind of ecological survey imaginable, bats, birds, bugs, reptiles and plants to ensure they donít run over a toad as they remove millions of tons of material and then ignoring the fact the after-use of the site is completely at odds with the surrounding eco-system.

Culled Cormorant
Culled Cormorant shown to have been feeding on trout.
Cormorant barbel
and feeding on barbel.

The third factor that has added to the inland numbers has been the colonisation of the continental sub-species sinensis. This bird is recognised as an inland nesting bird on mainland Europe and has quickly moved in to exploit the habitat provided by the newly created water bodies. This is not always the case as good old carbo is more than happy to spend as much time as he can snaffling roach miles up river if heís left to his own devices and undisturbed; accounting for the majority of our visitors.

The undeniable concerns of the fishery owners and anglers have been recognised by Defra with the introduction of the licensed cull where birds are proven to be causing damage. The cull is a national policy and the percentage of the population that is to be culled spread across the entire country. It is this very national element of the policy that in itself gives rise to the most significant problems. If for simplicities sake we work on the Cormorant population being 20,000 birds and the percentage to be culled is ten percent, giving rise to a figure of 2000. Defra then receive 500 applications to shoot Cormorants, it would then appear the culled number is divided by the number of licenses giving rise to four per licence. The more licences, the fewer birds each licence will be allocated. That is a very simplistic way to look at it but not that far from reality. My four licenses allowed me to shoot nine birds and with a population of over 250 currently on the river I will have to simply resorted to shoot to scare as itís not worth me doing the paper work. To keep this number of birds on the move is almost a full time job and the more people up and downstream chasing them back to me as I chase them off means hourly visits are needed when they locate the dace shoals. Shoot to scare does work it will scare Cormorants off along with the Bewicks, Widgeon, Black-tailed godwit, Lapwing and the remnants of the White-fronted goose population. It will also take two or three hours a day and cost a fortune as we have to use Bismuth at FORTY POUNDS a box, lead being banned within the SSSI/SAC. Youíre quite right, that would be bloody ridiculous better we get half a dozen gas guns and move them about the river. The end result is the same; no Cormorants, no Bewicks, no Smew, no Ruff.......enter the Avon valley desert.

To understand how this huge local imbalance has been created we have to add a fourth factor to our previous three. That factor is Natural England and some wildlife NGOís deliberately encouraging these non-indigenous species as previously mentioned but in this instance immediately alongside an SSSI/SAC where the impact of these birds is to have enormous impact on EU designated species. In some instances locally Natural England has given these isolated artificial theme parks a similar conservation status as the entire internationally important eco-systems of the Hampshire Avon River SSSI/SAC and the Hampshire Avon Flood Plain SSSI/SAC. Muddled thinking does not adequately cover this nonsensical thinking - I will not even consider cosy funding relationships - give me a day or two and Iíll think up terms to cover it!!

Having shown the ridiculous situation that has arisen how do we get ourselves out of it? Not easy I fear. Placing the Cormorant back on the quarry list would be one way but that would require legislation through the EU and I would be very surprised if anyone in Defra is going to support that. Cormorants above the NTL (Normal Tidal Limit as shown on OS maps) could be culled to a far greater extent. Difficult to monitor and regulate so it would appear unlikely. That leaves those living and working in the valley and the current regulatory agencies to do their job and get the situation rectified.

Natural England must get on and implement the existing legislation that is in place to ensure changes of regime on and neighbouring SSSI/SACs do not encourage species that adversely impact on the SSSI/SAC designated species. IE Those that actively encourage Cormorants and other species such as Sawbill ducks onto artificially created habitats, such as disused gravel pits, that eat thousands of EU designated species salmon, bullheads, lamprey etc on SSSI are acting illegally. NE is legally obliged to protect these designated species and they must be seen to actively and more importantly effectively implement this legislation.

Environment Agency fisheries division must actively put pressure on NE to control this situation. They must monitor NEís strategy and ensure it works. It would be a good idea to make this policy transparent to the thousands of frustrated anglers who pay £24,000,000.00 (twenty four Million pounds) annually to have their fisheries protected. In fact itís more than that as we also contribute through our taxes to the meagre GIA that the EA fisheries receive; we are one of the very few pastimes that pay the government twice for our privilege to enjoy our sport. It must not be left to individuals to chase those we pay in the agencies through the hoops of Europe with complaints to the European Commissioner for the Environment.

Both NE and EA fisheries must impress on the waste and mineral planning authorities that the mineral extraction companies and the water companiesí after-use plans do not put existing eco-system in danger. The current rush from the mineral extractors to leave a wetland void must have attendant responsibilities attached to this form of after-use for a minimum of a decade. Where islands are considered desirable they must ensure they do not afford sanctuary to potentially damaging species, many aspects of the current regime are in desperate need of an overhaul.

Mineral, water companies and all major land owners and managers must ensure their policies are thoroughly thought through and their actions do not give rise to subsequent problems. Encouraging every duck, goose and brown tweetie to come and take up residence, irrespective of what or whom they adversely impact upon is definitely not a good policy. That applies to species other than Cormorants, the equally obvious Goosander roosts and the valley goose population that now approaches a thousands birds. Canada and Greylags are not indigenous to the valley, the wintering White-fronts that we used to see now winter elsewhere. Itís not really surprising when the greylags and Canadaís have already had the best of the grazing. On the old country reckoning of four geese to a sheep, four sheep to a cow we have a flock of 200 sheep or fifty cows flying up and down the valley. I bet if you looked out of your window and saw 50 of your neighbourís cows come into land on your grazing youíd have something to say about it!!

Now the role of the fishery owners and the angling community, itís no good shrieking about the "bloody cormorants" if you are not prepared to help resolve the issue. By that I donít mean dusting off the blunderbuss and heading for the river blasting anything black with feathers to kingdom come. Not only will that be illegal but you along with the irresponsible dog walkers, canoeists, ramblers and fishery managers, shooting to scare, will do more harm than good; disturbing the wildfowl and waders we are trying to encourage. Where we must change our ways is that we must take a look at this situation from the viewpoint of Phalacrocorax carbo. Why is he steadfastly determined to head inland when he should be down at the coast eating flatties, eels and sprats? It means the harbour and estuary do not offer feeding of sufficient quality to sustain his or the populations needs. Alternatively the area has been over developed and disturbance drives the birds up the rivers to find undisturbed feeding.

If we assume that NE and the EA fisheries division has played its part and the planners will prevent further sanctuaries and inland roosts being developed. To add to this we must ensure the areas of feeding down at the coast as attractive to carbo as are our parr, dace and roach. To that end we must actively support and get involved with the efforts of others to create and extend marine reserves. We must become actively involved and support the efforts of others to minimise disturbance in the harbours. At the current rate we are adding moorings and increasing access on the water and land of our remote and wild places it can only end in disturbance and disaster. Fishery owners, angling clubs and organisations must work with the planners to ensure the needs of the river are recognised and reflected in the planning decisions. If you donít inform the plannersí decisions miles away down at the coast can reflect on your fishery and livelihood no one else will.

Having said all that itís a good idea to start the process at home and ensure our actions are not contributing to disturbance or damage to delicate eco-systems. Changes to the established regime might be difficult but only through looking through the eyes of others do we sometimes see the obvious.

Historic copy.

Seldom a day passes on the river bank when I donít have a conversation with one of the anglers related to the impact of cormorants or otters on our fish stocks. Certainly where stock is left exposed, without areas that afford cover and sanctuary, cormorants and otters can and do inflict damage. Forty years of the EA flood defence teams ripping out every fallen tree and overhanging branch has created a river of uniform blandness devoid of such areas of protection. I do not attempt to minimise the threat posed by cormorants and otters but highlight the fact that there are other factors that require similar attention.

The 1990ís is now established as the warmest decade since records began in 1660. This change in temperature is quite naturally to the benefit of some species of flora and fauna and is equally to the detriment of others. We have warmer water and higher nutrient levels from STW and agriculture, promoting weed growth and algal blooms. The impact of warmer water and increased algal growth on egg and juvenile fish is unknown and as such a concern justifying investigation. It may be that the actual biomass of the river may increase as can be seen in the rivers in warmer parts of the world. If that were to be the case we will inevitably see a change in the dominant species or even newly established species. What effect has the warmer water related to fungal infection on spawning grounds, particularly with the fungus covered rainbow escapees a common site on our fisheries? Disease carriers of the most obvious and high profile order yet we have a system that allows the majority of our rivers in low flow years to be directed through an intensive aquaculture system and expect the water to be free of contaminants when it is returned in an untreated flume back into the channel.

These same fish farms are acknowledged to act as huge predators, entrapment of migrating smolts requiring the screening of intakes, yet both salmonid and coarse fry populations that migrate within our river systems are still threatened if maintenance and inspection of these screens is not efficiently operated. Surely if we are serious about conservation measures the bypasses have to be foolproof.

It is generally accepted that cyprinids fare better than salmonids at times of high water temperature; this may well be born out if one compares the Avon chub and salmon populations. As far as I can establish the Avon chub population is at an all time high with well represented year classes throughout the length of the river. Bearing in mind the chubsí omnivorous habit, fry of any species would not be ignored as a food choice. The smallest carrier providing a stable environment for juveniles will usually also have one or two very large chub in residence, five and six pound chub are far from rare in the two meter wide carriers; any food source is soon exploited. Taking the all time high chub population and the low salmon population, I should also add low roach population is it perhaps more than coincidence? I do not advocate taking action against the chub, hopefully nature will swing the pendulum in the other direction to balance the equation. What would be of considerable interest would be a research project that shed some light on the interaction of our fish species and population dynamics.

Goosander onthe Avon
Hampshire Avon Goosander brood.

The beautiful Great crested grebe absent from the river 30 years ago, similarly goosander and Little egret then absent now breeding residents. We have over twenty pairs of grebe nesting at Somerley alone and if successful in rearing only one offspring annually that gives a population in permanent occupation in the order of fifty or sixty birds. Goosander, now recorded as a breeding species in Hampshire with a winter population in excess of one hundred birds. Goosander make cormorants look like beginners when it comes to emptying a gravel run of small fish. They work as a group in shepherding the fish into an exposed area before systematically picking them off in a most impressive demonstration of cooperation. Sixty, seventy a hundred, two hundred thousand small fish annually I donít know but such numbers must have an impact. Just what that impact might be is yet to be determined.

In the Mia Po Marshes in the New Territories north east of Hong Kong fish farming on a commercial scale co-exists with a cormorant population you have to see to believe. As for the cormorant population of the Avon valley it has continued to rise steadily over recent years for reasons that have yet to be scientifically determined. During the 60ís and 70ís cormorants were not an issue certainly upstream of Ringwood. Recent years have seen winter daily totals flying north of Ringwood well in excess of one hundred birds. Flatfish and eels in the lower river and harbour, that historically formed a large part of their diet, have become scarcer in recent years thus the birds have naturally migrated upstream to exploit fish populations within the river. The reasons behind the lack of their traditional food source once more remain to be determined, possible over fishing, pollution or habitat loss who can say but the end result is that we now have an additional one hundred plus cormorants flying in daily throughout the autumn and winter months to feed on our fish stocks. Even a conservative estimate of an individual birds daily capacity for fish at one pound and taking the number of birds at one hundred a grim picture starts to emerge. Fish from 3 to 12 inches, 1 to 8 ounces appear to make up the bulk of the intake in the region of 500 fish daily, given the duration of inland feeding perhaps sixty or seventy thousand fish.

Predated barbel
Autopsy result.
Mai Po Marsh
Vast biomass.

What are the restrictions that prevent population recruitment to compensate for even these high predation rates in our rivers? If we did have sufficient fish would we still be reluctant to share them with the species naturally dependent on this food source?

We are now seeing the welcome return of the otter throughout our river systems but this brings inevitable conflict with fisheries. We certainly have otters in the middle Avon that are successfully breeding and but for the incidents of road kill, to which otters appear remarkably vulnerable, the population would be expanding at a far more dramatic rate. Within the past six months on a five mile length of river I have picked up carp, salmon, barbel, pike, eels, tench and dace that have all been the result of otter predation. Not significant at the present level but if the record of a past keeper on the Avon at Somerley as contained in Brian P Martins, "More tales of the Old Gamekeepers" is correct, in that they killed as many as thirty a year, the current low levels of spawning stocks will be at risk. The numbers historically recorded at Somerley does indicate that the river is capable of supporting far higher numbers than are currently here. It is worth remembering that the period George Cole, the Somerley keeper who recorded those numbers, was working was also the acclaimed zenith of the Avon fishery. The real problem with otter predation results from the direction angling has taken in recent years as the pursuit of the largest specimen becomes the ultimate goal of many. These large fish have been transferred legally and illegally to may different fisheries where they make up the major attraction thus fishery financial viability. Many of these waters do not have the habitat to allow natural recruitment, when the introduced specimens have gone the fishery fails or requires considerable financial investment to replace them. Specimen hunting has seen the extremes of individuals basing their entire years campaign, for want of a better description, on the capture of one or two of these large fish. If "Tarka" then turns up and eats the fat old girl that is the focus of attention then resentment is bound to occur! Without a rethink of the angling ethos adopted by many, conflicts will be inevitable.

Otter predation
Otter kill.

I have long maintained this conflict would be in the main part resolved by means of a simple compensation scheme. In this age of DNA signatures being a cheap and readily available technique if Defra had a mind to set up such a scheme restocking becomes a less painful exercise for the fisheries.

Taken overall predation of stocks has increased dramatically in recent years, to put an accurate figure on the numbers involved or a percentage of the population is almost impossible given our present state of knowledge. What we can say without much fear of contradiction is that the increase in predation in recent years is in the order of several hundred percent. The issue is a very real one and is recognised through Defraís licensing strategy permitting a percentage of the Cormorant population to be culled as part of an overall fishery protection policy. If the impact of flood events, low flows, temperature implications and pollution in its many forms could be evaluated we might be in a better position to judge. Unfortunately we are a long way from unravelling that equation so the high profile, visible components tend to attract the major flack.