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Reducing Environmental Stress For Disease Prevention and Management

by Robert Fenner  

The role of stress; sources and degrees, in bringing on and solving marine livestock disease is not often fully appreciated. Weakening of specimens occurs most drastically in the course of wild collection, and holding, handling, and shipping of all livestock. What can we all do in our various roles as purveyors and custodians of this life? The purpose of this essay is to familiarize you with the nature of stress; its most common inputs, and address what you can and should do to ameliorate stressful conditions.

            Starting in 1982, I have presented talks on “three sets of factors that determine livestock health” at scientific gatherings, dozens of club and national gatherings, as well as three years of the University of New England “Fish Health Conference” in Biddeford, Maine.

Three Sets of Factors That Determine Livestock Health


As you can see, the second “set” of these factors entails “suitability of the environment”; all deviations of which can be accounted as sources of stress: Environmental, Social, And Nutritional and more with many subdivision therein.

            The complete “three sets” model other factor sets are “initial state” and “presence and degree of pathogenicity of disease-causing organisms”. These three factor sets interplay to determine livestock health. For here, this essay, we will limit our discussion to the role of stress in this fluid equation.


Introduction of Stress: Capture, Handling, Shipping

            Think about when outbreaks of disease are most likely to occur: during introduction of new livestock, particularly newly-arrived (wild-collected or captive-produced) stock is purchased. Indeed, all newly acquired livestock should be considered as carriers of infectious and parasitic diseases; and quarantined, perhaps prophylactically treated to avoid introducing troubles in your main display/s.

            I cannot over-emphasize the higher importance of everyone in “chain of custody” of livestock doing their part to reduce stress. Alternatively, chemical treatments for (induced) infectious and parasitic disease likely result in more deaths than cures. Put another way; once aquatic life, particularly marine, is over-stressed, there is little one can do to effectively recover its health.


Pathogenic Disease in the Wild

            Of course, nothing comes from nowhere; wild populations of fishes and invertebrates, plants and algae have resident bacteria, protozoan and more fauna that can become health threatening; though most exist in a balance that usually result in no symptoms of disease. Indeed, successful “symbionts” (“living together”) must need “get along” with their hosts/sponsors, less they both perish.

            On the positive side, aquatic organisms generally have enormous natural resistance (immunity) through their physiology; which in turn is mostly dependent on environmental factors. Divers do occasion naturally diseased life underwater in the wild, but by and large wild populations remain healthy due to their immunological defenses.

            The breakdown in the balance of health versus disease is mainly a matter of a shift in environmental conditions that weaken host life in favour of opportunistic endo- and ecto-organisms, as well as an increase in susceptibility to predation in nature.


Biological Diseases in Captivity

            Comparing life on land and freshwater environments, one finds that marines are far more susceptible to environmental variability. This makes sense intuitively as terrestrial organisms and freshwater biota live and have evolved in far more change-able worlds than the vast ocean realms. Though seawater habitats do indeed change; their shifts are almost always small and over long periods of time. Put in aquarist terms: sea life has little tolerance for environmental change; variances resulting in stress and loss of immunity.

There are several principal sources of stress that marine life encounters in our care: exposure to concentrated metabolites, low dissolved oxygen and RedOx, vacillating temperature, pH and specific gravity; poor and lack of nutrition, social traumas, and physical damage from handling….

            The worst of these insults occurs in the process of collection in the wild, and processing (handling and shipping) of collected and cultured stocks.

            More specifically, different sources of stress occur when livestock is:
Collected and moved: physical trauma from netting, being touched by hands; the sometimes use of real anesthetics or poisons in collection.
During Holding: Vacillation in water quality, burn from ammonia and poisoning from nitrite, nitrate accumulation; ill-effects of crowding and housing with agonistic life; lack of and mal-nutrition.
During Transport: Varying temperature; metabolite toxicity coupled with dropping pH, photo-shock.

            Having been in the trade for decades and reviewing the scant useful accounts of others observations on receiving livestock I will attest to the wide range of health in just-received shipments. Especially with long hauls (more than a day in the bag) and poor weather exposure the livestock may be outright mostly dead or on its way; all shipments experience light to severe physiological stress.

            Time spent in small volumes of water in bags during transport is most damaging; and careful consideration must be made in maximizing these variables versus the cost of space and weight in shipping cost. I have encountered pHs in the low sixes, and ten and more parts per million of ammonia. My stance and urging of the industry and hobbyists who are involved in long haul shipping of livestock to engage “guerilla acclimation” has also spanned decades of article writing and live presentations. Matching shipping water pH with water of no metabolite content and slowly dripping it to overflow to flush out metabolite before raising pH is absolutely critical in avoiding deadly hemolysis and gill burn.


Optimal and Stabilized Environment Is Key:

            Water quality values to shoot for include: pH of 8.2-8.4; alkalinity2.5-4 meq/l. No detectable ammonia or nitrite, Nitrate of ten or less ppm, esp. for reef life; high (7-8 ppm) and consistent dissolved oxygen; similar for RedOx (300-300 micro-Siemens/cm.); a specific gravity 1.025-26 (a bit higher for Red Sea, and sometimes artificially a bit lower for Fish Only systems).

            Other environmental factors to consider: Décor suitable and arranged to provide sufficient psychological cover and territorial relief; taking care to allow room for all and not stocking incompatible species, sex ratios or intolerant sizes of livestock. Avoid too-sudden changes in light/dark conditions.

            Nutritional considerations: Take care to assure all livestock is being “nitrified”; not just fed… as non-nutritious foods or wrong formats may lead to deficiency syndromes and further stress.


Environmental Manipulation versus Chemical Treatment Therapies:

            As mentioned to above; more often than not earnest “medicine” administration for marines proves toxic or inefficacious. Alternatively, simple environmental manipulation (pH adjusted freshwater dips/baths), raising pH….) will affect cures in not-too-far gone circumstances. In particular I find aggravating the continuing sale of unlabeled ingredient “cure-alls” and unscientifically proven “holistic” fixes that have no proven value as marine remedies.


The Power of Careful Observation

            There is nothing, no fancy test gear, no automated make up; high technology filtration or lighting that compares with the value of your observing your livestock and their behavior. Every time you’re near your systems you should be checking to see that all seems okay. Each time you feed your livestock or are working on the tank, is an opportunity to assure that all are present and doing well.

            Stress is a part of life, including those in our clear boxes of water; but too much stress leads to moribund organisms and their deaths. Note that there are always signs that something is going amiss in advance of real loss. The onus is upon you to catch such problems before they become deadly.



            The awareness and accomplishment of preventing undue stress in your livestock pays big dividends in assuring its health. Most new organisms are compromised to a degree from elements of their handling and shipping prior to acquiring them. To the extent that you are able to ameliorate sources of stress, your new and existing captive biota will thrive or fall prey to infectious, parasitic, nutritional, even simple environmental over-stress. As conscientious consumers we should do our part at all levels of distribution to investigate what species, from what areas do best; and further to do what we can once the livestock is in our care; observation and rest through quarantine; and if perceived necessary, treatment.

            I recall Stephen Spotte (1973) making a comment that seawater life forms were “physiological extensions” of their environment. Bear this in mind when casting your votes for buying, acclimating and placing new livestock.


Bibliography/Further Reading:

Fenner, Bob. Undated. Acclimating Marine Livestock for Home Hobbyists & Commercial/Guerilla Acclimation Technique. WetWebMedia http://wetwebmedia.com/acclimat.htm

Fenner, Bob. 2006. The three sets of factors that determine livestock health. TFH 11/06. http://wetwebmedia.com/mardisease.htm

Spotte, Stephen. 1973. Marine Aquarium Keeping. Wiley Interscience, NY. 171 pp.


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