Introduction
Fish are, by number, the most popular companion animals in the US.1 Fish are recognized to be important members of the human-animal bond, and more fish owners seek veterinary services for their fish with greater frequency. This is partly attributed to fish medicine expanding in the last few years from aquarium, aquaculture, and wildlife settings to include companion and ornamental fish like koi (Cyprinus carpio), goldfish (Carassius auratus), bettas (Betta splendens), and marine pet fish.
Wildfires are a component of western North American ecology, and many native wildlife and plant species are dependent on the renewing and nutrient cycling effects of wildfires.2 However, in the past decade, wildfire activity worldwide has increased on unprecedented scales, both in the number and size of incidents. With wildfire activity in western North America at historical highs in 2020 and showing no signs of improvement, it is increasingly important that veterinarians are familiar with evacuation, stabilization, and care standards for a variety of species that may be encountered in rescue efforts. In October 2017, the University of California-Davis Veterinary Emergency Response Team (VERT) and the Aquatic Animal Health Program (AAH) were called upon to evacuate several ponds of companion koi and goldfish affected by wildfires in Napa and Sonoma counties of California. Coordinators for VERT worked in close communication with first responders to ensure that evacuation areas were safe for VERT to enter and search for animals. Although VERT has provided veterinary support for disasters for > 20 years, the first time VERT was asked to evacuate fish from a disaster zone was in 2017. Members of VERT and AAH evacuated and housed approximately 40 fish from 6 different ponds from the Sonoma County wildfires zones in 2017. The successful rescue operations were publicized, and AAH and VERT were called to assist in subsequent fire seasons, evacuating 39 fish in 2018 and 137 fish in 2019 from fire zones.
Veterinarians interested in assisting in animal rescue work in wildfire disaster situations should seek out their nearest veterinary assistance corps, which are usually organized by state veterinary medical associations or local nonprofit organizations. Veterinary components of disaster response operations are usually built into an existing Incident Command Structure, which is a system designed to manage incidents on any scale, and veterinarians are advised to wait for deployment direction from their respective veterinary assistance corps and never self- deploy, because self-deployment can overwhelm and stress the response infrastructure and lead to unsafe situations. Veterinarians should be prepared to consider and manage several important factors (eg, human safety; fish-related water quality, handling, transport, housing, medical care; and other factors) while evacuating and housing aquatic patients during an emergency.
Human Safety
The safety of rescue personnel, evacuees, and first responders is paramount in any disaster situation, and it is essential for rescue personnel to receive adequate training about exposure to hazards and ways to avoid and respond to such hazards accordingly. Evacuation zones are often spatially close to, if not continuous, with active fire zones, and conditions in evacuation zones may change quickly and possibly lead to abandoning search and rescue missions. It is critical for rescue personnel to remain aware of surrounding conditions and be prepared with appropriate supplies and equipment, including personal protective equipment such as N95 respirators, eye protection, gloves, protective footwear (eg, steel-toe boots), and high-visibility clothing (Table 1). Common workplace health and safety hazards include confined spaces, extreme heat and cold, handling heavy equipment, musculoskeletal and respiratory hazards, electrocution, and heat stress and injury. Working in disaster zones is physically and emotionally taxing, and intervention is needed when individuals show signs of exhaustion, heat injury, dehydration, or emotional fatigue.
Recommended equipment and supplies for aquatic animal evacuations.
| Primary use category | Equipment or supply |
|---|---|
| Fish handling | Nylon sock nets of appropriate size |
| Nonpowdered nitrile examination gloves | |
| Neoprene diving gloves | |
| Large, catheter-tip syringe for ventilating fish | |
| Water quality | Waterproof thermometer |
| Waterproof pH meter | |
| Water conditioner (dechlorinator) | |
| Housing | Opaque stock tanks and appropriately fitted solid covers |
| Bicycle tire pumps that can be used as water tank aerators | |
| Plastic tubing and appropriately sized air stones | |
| Biosecurity and identification | Disinfectant |
| Record book | |
| Writing utensils | |
| Camera | |
| Human safety | Reliable and sturdy communication devices |
| Headlamps or flashlight | |
| N95 respirators | |
| Safety glasses or goggles | |
| High-visibility or reflective clothing | |
| Protective footwear |
Water Quality for Fish
Most fish affected by wildfires must be rescued because of dangerous changes in water quality in the wake of a fire. Large wildfires can deplete oxygen locally around ponds, creating acutely hypoxic conditions that can lead to the sudden death of fish. Ash particulates deposited in the water can cause damage to the delicate epithelium of gills and lead to respiratory distress, as well as reduce the surface area by which oxygen can be absorbed into the water column by coating the surface of a pond. Depending on the fire fuel type, ash can also be a major source of ammonium and nitrate deposited into water, which adversely affects water quality and fish health.3 The loss of aquatic life-support systems, such as pumps and filtration, is very common in wildfire zones and can lead to sudden and dangerous changes in water quality, such as increases in ammonia concentration, pH change, decreased dissolved oxygen concentration, and temperature change. Common pond species (eg, koi and goldfish) can tolerate short periods of decreased dissolved oxygen and are more tolerant of poor water quality than other ornamental species; however, sudden water-quality changes incurred in disaster situations are difficult for even the hardiest fish to tolerate. Stress induced by sudden water-quality changes typically manifests in affected fish as appetite and immune suppression, making them more likely to succumb to opportunistic diseases during rescue, transport, and emergency housing.
Water sourced for evacuation tanks should be as closely matched to home pond water as possible, especially for temperature. Depending on the path of the fire, fish may likely be temperature stressed before rescue and more vulnerable to further temperature shock than healthy fish. A study4 of stream temperatures shows that water temperature increased by as much as 7.8 °C in the wake of wildfire. Sudden changes in water temperature, even within a species’ optimal temperature zone, induce stress. In some instances, it may be possible to use some water from the home pond for transport if water quality is adequate. If outside water is necessary, the source (eg, wells or municipal systems) must be considered before the water is used. Municipal water sources contain concentrations of chlorine and chloramines that are harmful to fish and will need to be dechlorinated prior to use. This can be achieved by allowing water to off-gas in open containers for 24 hours or by adding chlorine neutralizers, which are generally available at pond supply and pet stores. An added benefit of chlorine neutralizers manufactured for ponds and fish tanks is that their formulations usually include polymer compounds to support the fish’s mucous layer and reduce external damage to fish during handling and transport.5
Handling
Detailed notes should be kept on the numbers of fish rescued from each pond along with the pond’s location and any known owner information. Descriptions of live and dead fish can be helpful for owners attempting to identify their fish. Photographic records are also useful and should be documented if the time and situation allow. It is important to limit handling as much as possible because all handling events are stressful for fish,6 and even gentle handling disrupts the fish’s mucus coat, which is critical for immune defenses. Over-the-counter products that can help support and protect the mucus coat during stressful events are generally available at pond supply stores and would be beneficial in evacuation situations. Nonabrasive nylon sock nets are ideal for handling larger fish such as koi. These nets are open on the end and allow fish to swim out of the net on their own without abrading their sides on the rigid frame of the net. Personnel handling fish should protect themselves and the fish by wearing nonpowdered nitrile gloves or neoprene wetsuit gloves. Some common pond-fish species (eg, Plecostomus spp) have barbs or spines that can injure handlers or get tangled in nets, and some fish varieties (eg, butterfly koi and butterfly goldfish) have delicate fins that can easily fracture during netting. Time out of water for fish should be minimized to reduce respiratory stress and skin desiccation.
Transport
Fish should be transported in opaque, dark tanks that are covered on top to reduce visual stress and the risk of fish jumping from the tank. The fish species should be considered when choosing the size of evacuation tank, and the water should be aerated during transport to prevent anoxia and suffocation of fish. The use of 100-gallon plastic stock tanks with 12-V tire inflators or bicycle pumps delivering ambient air into the water was ideal for koi transported by VERT and AAH. Transport times should be kept as short as possible to reduce the risk of ammonia waste accumulation and drastic temperature change. Stocking density in transport tanks should be kept as low as possible. Transport drivers should be aware of the weight of evacuation tanks when full, that the weight of full evacuation tanks in a truck bed will substantially change the way a vehicle handles around corners and increase the braking distance, and that standard truck suspensions and brakes may not be suited for evacuating fish in large volumes of water.
Biosecurity and Emergency Housing
Evacuation procedures and emergency housing should ensure that fish can be separated by ponds. Fish from different ponds should never be transported or housed together because of the risk of transmissible diseases like carp pox disease, koi herpesvirus (KHV) disease, and koi sleepy disease. Equipment used to evacuate fish and maintain housing tanks should also be pond specific, and careful disinfection protocols should be developed and implemented for staff tending to fish evacuees. Equipment that is in contact with fish or water should be regularly disinfected with appropriate in-date disinfection compounds (eg, chlorhexidine, iodophors, sodium hypochlorite, and hydrogen peroxide).7
Emergency housing water temperature and pH should match the home pond as closely as possible to reduce acclimation stress. In addition, activities around housing tanks should be limited as much as possible for the first 24 to 48 hours to reduce stress and prevent fish from bolting into tank sides and injuring themselves. If fish must be visualized during that initial acclimation period, opening tank lids quietly, slowly, and only as much as needed for assessment helps reduce bolting behavior. Many koi come from ponds that have low flows, and housing them in high-flow tanks may exhaust them as they swim against the heavy current. Tank flows may also need to be reduced while fish are acclimating, then gradually increased during the fish’s recovery period. During the acclimation period, “salting” the tanks can help reduce osmoregulatory stress on fish and allow them to allocate more energy to acclimation and immune function.8 Only salt products produced for pond use should be used. Other salt products, like those produced for swimming pools, may contain anticaking compounds that can be toxic to fish. We recommend gradually increasing salt concentration by approximately 1 g/L/d (part per thousand) until the pond salinity is maintained between 3 and 5 g/L. This salinity can be safely maintained for 7 to 10 days for most freshwater fish species. Salinity meters can be purchased at pond supply stores to guide salt treatment.
Fish evacuees may need to be housed for long periods following disasters. In our experience, fish owners had to wait for insurance inspections and payouts before rebuilding ponds and repairing life support systems, and it was not feasible to house large koi in small tanks for the duration of this rebuilding period. For some owners, such as those also allocating resources toward rebuilding their own homes, this process may take > 1 year. Local koi clubs are invaluable resources for alternative housing situations.
Diet
Typically, fish refuse to feed for the first 24 to 48 hours after a stressful event. Feeding during this period may result in excess organic waste in their housing tanks. During fish evacuations, we did not feed fish for the first 24 hours and then offered small amounts of high-quality commercial koi pellets gradually until fish were eating a clinically normal amount.
Medical Care
After 48 to 72 hours of acclimation, fish should be examined and screened for possible infectious pathogens (eg, Cyprinid herpesvirus 3 [also known as KHV] and carp edema virus [CEV]). We recommend anesthetizing fish for examination so that stress to fish is mitigated and safety for fish and handlers is facilitated. For most routine fish anesthetic procedures, we prefer the use of tricaine methanesulfonate buffered 1:1 (mass/mass) with sodium bicarbonate, with the anesthetic concentration in water dependent on the species of fish to be examined. For cyprinids, we prefer an anesthetic concentration of 80 to 100 mg tricaine methanesulfonate/L water, which moderately sedates the fish and enables safe collection of skin scrapes, gill clips, blood samples, and any imaging or ancillary diagnostic procedures that may be indicated.9 Optimal anesthetic concentrations for several other commonly kept species are available in the literature.10
In addition to primary pathogens of fish, including KHV or CEV, most illnesses in fish that practitioners are likely to see after an evacuation will be secondary, opportunistic infections. The mucus or slime coat of fish is their first line of innate immune system defense against pathogen invasion. The mucus coat is secreted by goblet cells in the epidermis and contains antimicrobial peptides, lysozymes, lectins, proteases, and mucins that function to block and neutralize pathogens, facilitate osmoregulatory functions, and foster certain social and reproductive behaviors such as nest building and defensive behaviors.11 Although the mucus coat is sloughed and replenished constantly, it is at risk of acute mechanical injury. Excessive handling, inappropriate netting or transport materials, and abrasion against tank sides or substrate are common ways of damaging the mucus coat in evacuation settings. Anywhere that the mucus coat is damaged or compromised creates an opening for pathogen invasion and osmoregulatory dysfunction.11 Measures to minimize handling combined with the use of mucus coat–friendly handling practices when handling is necessary can greatly protect this critical immune system component of the fish and reduce opportunities for infection with secondary pathogens.
Reducing and mitigating environmental stressors in emergency housing settings can help prevent outbreaks of disease in fish recovering from evacuation and transport. Acute stress enhances the effects of the innate immune system through activation of the sympathetic nervous system; chronic or compounded stress events lead to the production of corticosteroid-releasing hormones, catecholamines, and glucocorticoids to modulate the response of the hypothalamus, which is the central processing organ for stress responses.12 These hormones activate the hypothalamus-pituitary-interrenal axis in an attempt to regain homeostasis.13 In fish, this neuroendocrine stress response is energetically costly and draws metabolic energy away from the immune system, leaving fish more vulnerable to secondary infections.12
Viral diseases
Viral diseases are of critical import if fish from different ponds are housed in the same facility. Viral pathogens, such as CEV and KHV, can have devastating impacts on naïve populations and are easily transmissible in water or on fomites shared between tanks. Additionally, KHV can reactivate from its latent phase in carrier fish and cause high morbidity and mortality rates in stressed fish.14 Diagnostic viral screening panels are available for cyprinids, and we recommend that samples from a representative population of each pond be submitted, if possible, to help ensure that viral diseases are not brought into a rescue facility or that fish from virus-positive ponds are kept secured from naïve fish. The American Fisheries Society’s Fish Health Section Blue Book15 provides guidance on the number of fish to select for sampling to maximize the possibility of detecting pathogens in a given population. Viral diseases with low mortality rates are also important because they can recrudesce among stressed fish. Viral diseases like carp pox diseases (Cyprinid herpesvirus 1) and lymphocystis disease (lymphocystis disease virus 1) commonly recrudesce in times of stress and cause characteristic skin lesions.16 Although carp pox and lymphocystis disease are not typically associated with death, these viral diseases substantially contribute to immune suppression and epithelial defects that make fish more susceptible to bacterial and parasitic infections.
Bacterial infection
Several important mechanisms against bacterial infection have developed in fish species, including the thick mucus coat (embedded with antimicrobial peptides) and a well-developed innate immune system.17 Bacteria commonly associated with disease in pond fish (eg, Flavobacterium columnare [columnaris disease], Pseudomonas spp [ulcer disease], and Aeromonas spp [furunculosis or septicemia]) are ubiquitous in aquatic environments.10 Proper disinfection of housing tank water (eg, with UV or ozone treatment) can reduce the bacterial burden; however, disease management should focus on optimizing fish immune health, rather than removing bacteria from the environment. Signs of bacterial infections in fish generally include erythema around the fins or ventrum, exophthalmos, loss of appetite or anorexia, lethargy, or change in gill rate and effort, alone or in combination.10 Some bacterial diseases like columnaris disease can be diagnosed on characteristic findings on clinical examination, whereas others require bacterial culture to identify the causative agent. Although multiple antimicrobial options are available for the treatment of clinically ill fish, antimicrobial use needs to align with applicable regulations pertaining to antimicrobial use and drug residue avoidance in fish because there may be no regulatory distinction between commonly kept pond-fish species and their aquaculture counterparts (eg, Cyprinus carpio produced for display or human consumption).
Parasitic disease
Parasitic disease is frequently encountered in fish medicine, and many pond fish have a mild burden of ectoparasites that do not cause clinical disease. Many ectoparasites, such as Ichthyobodo spp, Ichthyophthirius spp, and Gyrodactylus spp, can be diagnosed with a skin scrape or gill clip examined under light microscopy.10 We recommend viewing wet mounts of skin scrapes and gill clips under bright field and phase contrast, as phase contrast sometimes allows better visualization of transparent microorganisms than does standard bright field. It is helpful to quantify ectoparasites present, and we recommend treating even minor parasitic infestations in evacuated and recovering fish stable enough for antiparasitic treatment; doing so would reduce parasitic stress and immune systems burden. Depending on the parasite diagnosed, there are multiple parasite treatments available.18 Many of these treatments (eg, formalin and potassium permanganate) have exposure risks for handlers and should be used only by appropriately trained individuals with proper personal protective equipment. Discharge of these chemicals is generally carefully regulated, and practitioners should be familiar with these regulations before prescribing treatments that will result in chemical discharge.
Fungal and fungal-like infections
Fungal infections tend to be by secondary pathogens and appear around sites of epithelial damage. The water mold Saprolegnia spp is the most commonly encountered secondary fungal-like pathogen in freshwater pond fish, in our experience. Saprolegniasis usually causes cottony, white growths on the skin and gills.10 The use of the aforementioned salt treatment and mitigation of environmental stressors will reduce a fish’s risk of developing saprolegniasis. For instances in which practitioners encounter saprolegniasis, it is important to investigate underlying diseases (eg, viral and bacterial diseases) in addition to addressing the fungal infection.
Noninfectious diseases
Trauma to fish commonly occurs during transport or while fish are familiarizing themselves with their new enclosure. Scale loss can occur if fish are handled excessively or without proper precautions. It is important to consider that scales arise from the dermis; thus, scale loss results in ulceration and exposure of deeper epithelial tissues to pathogens in the water column.19 The use of topical treatments to speed healing (eg, Manuka honey) may be considered during physical examinations to aid in minimizing osmotic stress resulting from ulceration.20 Injuries should be carefully monitored during the acclimation period to ensure affected fish do not develop signs of secondary bacterial or fungal infection at the site of injury.
Veterinary Impact
Veterinary medical expertise is essential in disaster responses involving animals. Underlying illnesses, including reproductive disease or latent viral infections, may become more apparent in times of stress, and fish may show signs of acute or chronic diseases. Rescuing and housing aquatic animals in a disaster situation requires planning and staging that is typically not required for terrestrial animals. Aquatic animals often require extended periods of emergency housing after evacuation and rescue networks should account for this before rescuing aquatic animals. Nonetheless, fish are an important part of the human-animal bond and are treasured companions to their owners. The feedback we received from our efforts to rescue fish in the wake of wildfire in northern California was overwhelmingly positive and enthusiastic. By being prepared for evacuating and housing fish patients, veterinarians can play an important role in the emotional recovery of fire victims and the welfare of these aquatic animals.
References
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Stevens BN, Michel A, Liepnieks ML, et al. Outbreak and treatment of carp edema virus in koi (Cyprinus carpio) from northern California. J Zoo Wildl Med. 2018;49(3):755–764.
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Parker-Graham CA, Lima KM, Soto E. The effect of anesthetic time and concentration on blood gases, acid-base status, and electrolytes in koi (Cyprinus carpio) anesthetized with buffered tricaine methanesulfonate (MS-222). J Zoo Wildl Med. 2020;51(1):102–109.
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Wainwright DK, Lauder GV. Mucus matters: the slippery and complex surfaces of fish. In: Gorb SN, Gorb EV, eds. Functional Surfaces in Biology III: Diversity of the Physical Phenomena. Vol 10. Springer; 2017:223–246.
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Nardocci G, Navarro C, Cortés PP, et al. Neuroendocrine mechanisms for immune system regulation during stress in fish. Fish Shellfish Immunol. 2014;40(2):531–538.
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Mateus AP, Power DM, Canário AVM. Stress and disease in fish. In: Jeney G, ed. Fish Diseases: Prevention and Control Strategies. Academic Press; 2017:187–220.
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Lin L, Chen S, Russell DS, et al. Analysis of stress factors associated with KHV reactivation and pathological effects from KHV reactivation. Virus Res. 2017;240:200–206.
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Fish Health Section Blue Book. American Fisheries Society. Accessed July 31, 2021. www.units.fisheries.org/fhs/fish-health-section-blue-book-2020/
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Crossland N, Hawke J, Del Piero F, Sokolova Y, Waltzek T, Viadanna P. Investigation of a cyprinid herpesvirus 1 disease episode in a group of pond-reared koi. J Aquat Anim Health. 2018;30(3):185–190.
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Guide to using drugs, biologics, and other chemicals in aquaculture. American Fisheries Society Fish Culture Section. Accessed July 31, 2021. https://fishculture.fisheries.org/working-group-on-aquaculture-drugs-chemicals-biologics/wgadcb-resources-tools/guide-to-using-drugs-biologics-and-other-chemicals-in-aquaculture
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Ang J, Pierezan F, Kim S, et al. Use of topical treatments and effects of water temperature on wound healing in common carp (Cyprinus carpio). J Zoo Wildl Med. 2021;52(1):103–116.
