Question:
What are the less obvious signs of stress in a fish? Diseases, death,
changes in activity level, being less colorful, not eating, rubbing
against things, labored breathing are the readily apparent ones, but if a
fish was showing none of these signs, would there be any other
indicators?
Answer:
That's already a pretty complete list you've provided. You are going to
make us work to give more symptoms.
i) Reflection, viewed at an angle, are their scales as reflective (or
matt) as their sibling's
ii) Transparency of the rays, especially the caudal fin. During
prolonged stress, the fins may develop a slight transparency (loss of
opaqueness ?) starting at the base moving towards the tips of the fin.
iii) Fin clamping
iv) Cloudiness over the eyes.
v) Colour of the gills.
vi) Different swimming depth in tank as compared to siblings.
vii) Trouble maintaining orientation.
Checklist of Behavioral Signs That May Indicate Stress in Fish and Marine
Animals
· Understand "normal" behavior first and look for deviations from that (be
alert to early "subtle" changes)
· Color changes, such as those caused by drops in salinity in saltwater
tanks, not associated with feeding or mating, or diurnal changes
· Frayed or "eroded" edges of fins
· Clamped fins instead of fully displayed fins
· Fully rigid fins instead of fully displayed, rippling or undulating fins
· Resting on the bottom or "nose up" gasping near the surface instead of
spending some time in mid-water portions of the tank
· Remaining suspended exclusively in one location of the tank without
movement and without feeding, often with other tankmates approaching
cautiously and showing an interest, but ultimately leaving the subject alone
· Yawning
· Slime spots, white spots, red spots
· Cloudy or "bubbled" eyes (possibly due to high pH or supersaturated
water)
· "Flashing" or scraping against rocks, logs or other hard tank decor
· Flared or enlarged gill covers
· Repeated rapid, jerky, evasive-like motions instead of "relaxed" swimming
· Lethargic movement (often from overfeeding)
· Distended or shrunken bellies
· Reluctance or refusal to feed (possibly high nitrate concentrations in
the water)
· Rapidly expelling ingested food with reingesting it, especially if the
same food is normally eaten
· Bruised or blotched skin or lips or "noses"
· Dislodged scales
· Fish at rest in a curled or "cramped" position
· Constant aggressive interaction between tankmates, creating physical
damage, parts missing, damaged areas near gill covers or "ears" of lobed
fishes
· Aggression bouts or constant butts and charges and parrying associated
with a particular territory or sheltered location (not enough hiding places
or territorial locations)
· Rapid gill movements (possibly increased ammonia levels)
· Rapid, seemingly uncontrolled movement when the light fluctuates, when
there is motion by people just outside the tank (especially if such
distractions or "triggers" occur unpredictably and haphazardly over time)
· Congregating of fish of various species in a specific area of the water
column, and other than "normal" schooling behavior of the same species (such
as to avoid being near activity outside of tank or to avoid the territory of
a highly aggressive tankmate)
· Chronic fading or disappearance almost entirely of pattern or color
(bright light over extended periods of time and the lack of overhead
cover-failure to provide day-night lighting schedule)
· Color loss-a classic sign of stress, as well as almost all other diseases
(color loss or darkening indicates fish is under stress and possibly is
already sick)
· Repeated attempts to "escape" at the surface after being acclimated to
covered tank conditions
· Susceptibility of multiple species and numerous individuals to lateral
line or "hole-in-the-head" erosions
