Fry SalvageSubmitted by Joe Kambietz, here is information to help interested individuals who come across stranded salmon fry during times of low water flow.
Often young salmon become isolated and stranded in small pockets of water that is going dry. These fish may die here if they are not saved and put back into the main stream. This is what fry salvage is.
There are many reasons why these fish become trapped. They may have taken refuge from high water by going into a slough or side channel. The attraction of food or water flow can attract them into irrigation ditches, or perhaps it hasn't rained for some time and the creek is drying up, leaving its fish stranded in isolated pools. Salvaging these fry is a simple and satisfying project that can significantly help increase the productivity of the stream. When considering a fry salvage project, which always seem to be an unforeseen event, we must look quickly and carefully at the situation to determine the exact state of the emergency. Fish that are caught in isolated pools face many hardships, any of which will eventually kill them. These are:
- Lack of oxygen- Young salmon need above 6 parts per million to thrive. The stoppage of surface stream flow generally means that the oxygen could all be used up by the trapped fish and they will die. Check O2 levels. Quite often in the side channels and intermittently connected sloughs have water moving into them through the gravel so oxygen may not be an immediate problem.
- Temperature- When most bodies of water dry up, the last remaining areas will tend to be open and exposed. Without the continual addition of moving stream water these pools heat up quickly. Salmon can only withstand temperature to 20o Celsius for short periods of time. The warmer the water the less dissolved oxygen it can hold. Water at 20o has only 9 parts per million oxygen under ideal conditions. Just a few fish in a pool could quickly remove enough of this oxygen for them to all die.
- Food- Young fish require a considerable amount of food. Even though they can live for quite some time without it, they will eventually die. If they are trapped for an extended period of time and are lucky enough to survive, their growth will surely be stunted and once rejoined with the main flow they will have a hard time competing with the larger fish in the stream.
- Predators-The dry stream bed or side channel is a perfect pathway for any creature looking for a meal. Birds of all sorts and many mammals routinely feed in isolated pools where stranded fish are easy targets. The difference noted between two pools where fish survive in one and are preyed upon in another could be as simple as a branch lying on the bottom. Where there is a hiding place, fish can survive.
Now that we have concluded that our stranded fish are in dire need we must formulate a plan. This plan need not be complicated. Some of the following questions might help.
- Do I need to catch these fish?- Maybe a little shovel work can reconnect the pool to the main stream thereby letting in cool, oxygen rich water and these fish will survive well here until the next high water event. Perhaps you might add a branch or two for cover is all that is needed.
- How will I catch these fish?- You will need a seine net, pole seine, dipnets, and an electroshocker. The less disruptive to the pool and the least amount of stress on the fish is the best way. Remember these fish will be in a sorry state already with high temperatures, low oxygen, no food. Anything you might do like muddy the water or chase them around could kill them. You may also catch these fish with baited Gee Minnow traps, for this technique, refer to Streamkeepers Module 1, Juvenile Fish Trapping and identification.
- When I catch the fish what will I do with them?- The simple approach would be just to release them as quickly as possible into the same stream. Some consideration should be given to how crowded the receiving stream is already. Given that lack of water has partially dried up the system perhaps you'll overcrowd another area. With limited food and habitat no more fish can be produced in a place that has too many fish already. You could plant them into another tributary of the same stream that's not overcrowded; perhaps you could place them above an impassable barrier in the stream where no fish are. Be cautious this last option requires a transplant approval. Or perhaps you call bring them back to a hatchery that's located on the same stream to be smelted or at least raised until the fall rains occur and the stream returns to full flow. These fish are indeed special. Their parents survived all the hazards of the open pacific to return and spawn in your stream. The few fish that survived the incubation in the gravel and early stream rearing are part of a continuum, a long line of genetically unique fish that the artificial condition in a hatchery cannot produce or replace.
Concern for safety is essential when working outdoors and in remote areas. Always tell someone where you are going and when you will return. Never work alone; carry emergency phone numbers and a cellular phone if you are able. Supervise all children closely around any body of water. Carry a small first aid kit if possible. Do not attempt to wade fast flowing water or into water above your knees. Watch out for the slippery streambed, it can sprain ankles and twist knees. Beware of undercut banks and especially fast flowing areas. Buckets full of water and fish are heavy do not lift with your back. When carrying heavy loads get help. To ensure your safety get permission to cross private property and remember the dry streambeds and side channels are like roadways for wildlife and domestic stock. Beware of bears as they feed on scrap that remains caught in the brush during high flows or feed on overhanging berries. Make noise; carry a bell and bear spray if you are working in these areas.
- On a small scale this is a fairly simple project. If it starts to involve very large area and big numbers of fish a little time spent in planning and co-ordination will go a long way. Your community advisor will be of help. No permission is required to salvage small numbers of stranded fish and release them further downstream in the same stream system; however, removing any amount of fish from the stream and transplanting them to another stream or upstream of a barrier will require a permit. Likewise transplanting captured fish to a site where they will be held, fed and cared for will need approvals; again your community advisor will help obtain and co-ordinate approvals for you. Always, Always let the authorities know what you are doing. Take time to call Federal Fisheries and Provincial Fish and Wildlife and let them know where you will be working and when. If this is the first time you have rescued fish, contact the authorities for somebody to give your plans a check. Once this contact is made and the ground rules are figured out it will make future rescues easier and not required official visits. Remember that these people have a lot to do without coming out with the red light flashing to check up on you.
Effort and time of the Year
The personal effort on a fry salvage project can be substantial. Generally the drying up of a stream or productive habitat takes everybody by surprise. This condition is likely to happen in the heat of summer when everybody's on holidays. Also scrambling up and down dry streambeds in the heat of summer with big buckets of water and fish can be exhausting. In short, the effort is generally this side of panic with not much planning, and a whole lot of sweating. Start to think of salvage after every inordinate high flow in your stream and during dry hot spells. An unexpected flood will drive fry into side channels and off channel ponds when the main stream is in flood. The quickly dropping water will strand these fish. The critical time for fry salvage is in the warm summer months.
- Capture Equipment
- Dip Nets - of all sizes
- Pole Seine
- Beach Seine
All dip nets and beach seines should be small enough mesh to capture fish from 1" to 8" long. Please note that the mesh should be from 1/8 to 1/4, less than 30 feet in length and less than 3 feet deep. This is a very specialised net that you will not find anywhere. If you think you might be doing fry salvage find out who has these specialised nets before hand and arrange to use them in an emergency. Good sources are Fisheries and Oceans, any biologist doing fieldwork studies or the Fish and Wildlife Branch as they use the same sort of equipment. Fish hatcheries and even your community advisor may have one or know where there is one. Pole seines, which are a small piece of net, generally less than 8 feet long and attached between two broom handles, are fairly quickly improvised, however, don't let that stop you from making good ones ahead of time that have a lead line and a few corks on them, just in case.
- Do not consider using an Electroshocker unless there is a certified trained crew and a well-organised plan. Electroshocking although effective is a very dangerous practice. It immobilizes the fish by passing an electronic current through the water and fish and knocking the fish unconscious. If you think the use of an Electro shocker on your project is justified consult your Community Advisor for an opinion before proceeding further.
- Bucket, buckets and more buckets of all sizes.
- If transport is required out of the stream to another location by a short distance (less than 15 minutes), it can be accomplished with garbage cans and battery powered aerators. If the numbers and distance require it, use a transport tank on a truck or trailer with the ability to aerate with oxygen. When healthy fish are moved from a controlled environment a safe loading rate in the tank would need to be about one pound of fish to one gallon of tank volume or about 100 grams of fish per litre.
- However, these are very stressed wild fish being chased around and moved, give them lots of room. Try loading less than one quarter pound per gallon or 25 grams per litre.
- Using a large transport tank is good if you can conveniently load it with water.
- It should be cool; not so cold as to give the salvaged fry a thermal shock, but definitely colder than the warm water they are coming from. Moving fish quickly to water of another temperature than what they came from is very stressful for the fish and given a big enough difference it could kill them. Putting fish in a lower temperature is less harmful than putting fish to warmer water. So how much can this difference be? Don't put salvaged fish into water more than 4 degrees lower.
- The water in your tank should be super saturated with oxygen before the fish are put in. These fish have been chased and herded in a shallow muddy pool, put into small buckets and carried 15 minutes to a transport trailer at this point they and you are breathing heavily. Fish that have an oxygen deficit can remove the oxygen from the tank water faster than the airstones can put it back, and then they die. Starting off with a super saturation can avoid this unfortunate possibility. How super saturated? 12-18 parts per million in the tank will be sufficient, do this before the fish arrive of course and have some way to measure dissolved oxygen in the tank along with you.
- Polaroid sunglasses, a broad brimmed hat, waders, gum boots, fry identification guide, thermometer, 02 meter, sample bottles, good pocket knife, cell phone, first aid kit, bear spray, and a camera. Some of these could round out your equipment list.
- If you decide, because of your observations to leave the fish in the isolated pool until the next expected high flow will release them then the very least you should do is return and check frequently to se if the conditions haven't changed for the worse and you fish are still thriving.
- If you decide to reconnect the pocket of water with the mainstream then if possible dig the incoming trench first. Start at the source, the stream, and dig the trench down hill to the isolated pocket. Going the other way round creates a lot of extra work. Once the water starts flowing into the pocket that's holding the stranded fish it will fill and overflow downstream showing where you should dig and consolidate the outgoing trench. This ditching need not be a huge operation; a small well-planned trench can move a lot of water.
- The material that you place in the pond for cover is for the fish to hide under, out of the sight of predators. Ideally the material should be complex and slightly away from the bottom of the stream. For example, a live branch from a cedar tree held down with a stone would be superior to a short chunk of log with no branches. Place a few of these strategically where the holding fish can benefit from seeping inflows or perhaps in deeper shaded areas. Avoid placing a lot of transient debris in the stream that will be moved downstream in the next flood event and cause a destructive dam downstream. Don't be afraid to join a whole string of pools together by ditching. You will find that in many instances a good portion of the fish that are stranded will leave these pools under the cover of darkness and find their way out. This is certainly the ideal condition you would like to create.
- If you decide to transport the fish out of the pools, have a short term plan on who will be catching, who carries and where the path will be to the release site. You should have a basic understanding that you are not releasing your salvaged fry into an overcrowded situation where they will not survive. Lastly, the release site should be a quiet area that will allow these fish that you have chased and caught in muddy, hot, oxygen impoverished water to regain their senses before being battered about in the current or sent drifting helplessly downstream into the jaws of some waiting predator.
- Fill the buckets with clean water before you try to capture the fish.
- Don't put too many fish per bucket. Remember 1 250-gram, half pound trout uses approximately the same amount of oxygen as would 50, five-gram coho fry (50 x 5=250).
- Don't leave the fish too long in the transport pails.
- Keep the buckets covered and dark to reduce stress on the captured fish.
- Try and balance your load, a half-bucket in each hand is easier to handle than a full bucket carried in one hand.
- If you decide to transport these fry, calculate how many fish you can transport in your tank. Have some way of replenishing the oxygen in this tanker and some method of measuring the oxygen in the tank. Have water in your tanker before you start to corral and catch the fish. Also have a supersaturated condition in this water, particularly if you are transporting large numbers.
- Have a plan on where these fish are going; what's the release plan? Try not to dump them all at one site. If they are going to a hatchery for rearing, the transfer of disease is a concern. These incoming fish should be isolated from all other stocks for a short time or maybe the duration of their rearing. Being wild fish they should not be marked in any way that would identify them as regular hatchery fish. Also they may be mixed species and sizes that you might want to sort out before you release them back into the stream. Work on a release plan that offers the best hope of survival for these fish that will benefit your stream most.
- Lastly, keep records of your experience this season, surely you can expect it to reoccur. Keep an account of what was done, by whom, where and with what equipment, and the effort taken. What species were involved, what size they were and what was done with them. You can develop a very good plan for a salvage operation for the following years.