How Stress Can Affect Your Fishes’ Health
Stress is a critical factor in fish health. It is so important, in fact, that scientists have studied it in detail, both in the wild and in captive fish. Stress is a very complicated subject that permeates every aspect of fish-keeping.
'Stressors'
The primary rule to remember with stress is that, as the saying goes, prevention is better than cure. The things that cause stress in a fish’s life (“stressors”) include overcrowding, handling, a poor or unfavorable environment, inappropriate or aggressive fish sharing the same tank and, in the wild, predators. All of these (and others) cause fish to react in different ways depending on the type and amount of stress.
Fish have evolved and live in a relatively stable environment. Their stress responses are consequently better at handling short-term trouble and are not as well-suited to long-term environmental stressors. Unfortunately, both types of stress can cause problems.
Short-term Stress
For short-term stress, the most common reaction is one everybody recognizes -- to flee from danger. In the wild, the cause is frequently a predator. In captivity, it can be a net that causes the reaction, as the keeper tries to capture a fish for closer examination or transfer to another tank.
When a fish senses this kind of danger, it triggers a short-term alarm reaction by releasing hormones, including adrenalin for its locomotory muscles. This will give it a shot of energy to escape quickly. The fish also releases cortisol. Problems occur because the fish’s body exchanges long-term health for a short-term boost to relieve the cause of stress -- the adrenalin disturbs the fish’s natural osmoregulation (the balance of salt and water in its body) and the cortisol affects white blood cells and reduces the effectiveness of the immune system.
Once the panic has passed, the fish must also regain its natural balance. This can take hours or days, even after only a short period of stress.
Long-term Stress
Long-term changes, such as a poor or unsuitable environment, are handled with the same initial response – an alarm message to escape. However, if escape is impossible, the fish does not stop being stressed: it begins to adapt to the new environment as best it can.
At first, the fish’s body tends to overreact but, with time, it will adapt to reach the best possible balance – physiologically and behaviorally. Throughout the period of adaptation, the fish still prioritizes reacting to the new environment and remains stressed, so its immune system suffers and it is prone to disease. Adaptation normally lasts from four to six weeks.
However, if the fish continues to be in stressful conditions, such as a constantly deteriorating environment or endless bullying from aggressive tankmates, it continues to try to adapt and extends all the bodily responses as long as necessary. This reduces its chance of survival. In the worst possible situation, where adaptation to the new environment is impossible (such as putting marine fish in fresh water), the fish will exhaust itself fatally.
As a fishkeeper, it is extremely important to consider the effects of stress. Planning ahead, careful control of the environment and management of the fish population are fundamental basics in fishkeeping. Less stress means less disease.
FAQs
For example, stressors increase the permeability of the surface epithelia, including the gills, to water and ions, and thus induce systemic hydromineral disturbances. High circulating catecholamine levels as well as structural damage to the gills and perhaps the skin are prime causal factors.
How does stress affect fish reproduction? ›
Low levels of stress may have a positive effect on reproductive processes while greater stress has negative effects on fish reproduction. The concept of hormesis is a useful way to think about the effect of stressors on fish reproduction since responses can be nonmonotonal, often biphasic.
What is the role of stress in fish disease? ›
Stress impairs the production and release of antibodies. Tempera- ture stress, particularly rapid changes in temperature, severely limits the fish's ability to release antibodies, giving the invader time to reproduce and overwhelm the fish.
What are the stages of stress response in fish? ›
There are three main stages to the stress response: alarm, resistance, and either compensation or exhaustion (death) (Selye, 1950, Schreck, 2000). The nature (magnitude and duration) of the stress response is dependent on the severity and duration of the stressor.
What are the stress indicators in fish? ›
Cortisol in Fish
Cortisol is a reliable stress indicator produced by the adrenal cortex in the adrenal glands in vertebrates and is considered the major stress-related hormone in teleost fish [14].
What happens when fish are stressed? ›
Strange Swimming: When fish are stressed, they often develop odd swimming patterns. If your fish is swimming frantically without going anywhere, crashing at the bottom of his tank, rubbing himself on gravel or rocks, or locking his fins at his side, he may be experiencing significant stress.
Does stress stunt fish growth? ›
Fish development and acclimation to environmental conditions are strongly mediated by the hormonal endocrine system. In environments contaminated by anthropogenic stressors, hormonal pathway alterations can be detrimental for growth, survival, fitness, and at a larger scale for population maintenance.
What reduces fish stress? ›
The best way to prevent or reduce fish stress is to provide them with a healthy environment. That includes stocking the tank with the right amount of aquarium decorations and having the proper aquarium supplies. You want to ensure that they are receiving the proper fish care that minimizes triggers.
What is stress in fish farming? ›
Stress is a normal reaction of the organism to a perceived or potential danger, in which the bodily processes prepare for “fight or flight”. Throughout their lives, farmed fish usually undergo various stressful episodes.
How is fish stress avoided? ›
By maintaining fairly consistent water conditions, your fish will not become stressed. Three nitrogen compounds, ammonia, nitrite and nitrate, have varying degrees of toxicity and can be stressful at all levels. Ammonia can be toxic in low concentrations and severely stress fish under any concentration.
Short-term stress will cause an increase in heart rate, blood pressure, and respiration. The fish is reacting much as we do with the fight or flight mode. The fish can only maintain these altered states for a short period of time and then they will adapt, or the stress will become chronic.
How long does it take for a fish to recover from stress? ›
For example, fish suffering acute stress response due to low oxygen levels caused by a filter failure may recover in a matter of hours once proper oxygenation is restored. Fish that have suffered chronic stress may take longer to recover, especially if they've developed a secondary infection.
What hormones do fish produce during stress? ›
In fish, cortisol also has an osmoregulatory function (Eddy 1981). The other major endocrine response to stress in fish is the secretion of catecholamines, primarily adrenaline (epinephrine), from chromaffin cells following sympathetic stimulation (Mazeaud et al.
Can fish sense stress? ›
Anatomical, pharmacological and behavioural data suggest that affective states of pain, fear and stress are likely to be experienced by fish in similar ways as in tetrapods.
What is environmental stress in fish? ›
Stressors are environmental factors that cause stress. They include biotic factors such as food availability, the presence of predators, infection with pathogenic organisms or interactions with conspecifics, as well as abiotic factors such as temperature, water availability and toxicants.
Does fishing stress fish? ›
Humanely Catching Fish
The more stress a fish experiences while being caught or landed, the more lactic acid builds up in its muscles and the more cortisol (stress hormones) it produces in its blood -- which can have a negative impact on the taste of the fish.
How does stress affect reproduction? ›
High cortisol levels can disrupt the balance of other hormones, including key reproductive hormones like estrogen and progesterone. A hormonal imbalance can interfere with ovulation and your menstrual cycle and make it more difficult for you to conceive. Stress can also cause irregular menstrual cycles.
What are the factors affecting fish reproduction? ›
The factors that affect fish spawning include temperature patterns, amplitude and phase shift of temperature variations, and winter and spring temperature fluctuations. The factors that affect fish spawning vary with species and are intricately linked to species-specific ecology.
How does stress affect reproduction in animals? ›
Environmental factors, infection, malnutrition, and chronic strenuous activity can all lead to alterations in reproductive functionality in animals. Stressors interfere with timing and regulation of reproductive hormones and processes, such as gonadotropin-releasing hormone (GnRH), luteinizing hormone (LH), and others.
How does environmental stress affect animal reproduction? ›
Solar radiation, wind speed, air temperature and humidity are all factors which are concerned with the presentation of heat stress. An early reproductive responses to heat stress are the decrease in the intensity of estrus and consequently low fertility [3] .
