Flash photography and fish

Behavioural and pathomorphological impacts of flash photography on benthic fishes,
Research paper by Curtin University published: 24 January 2019

Our study showed that effects of photographic flashes are negligible and do not have stronger impacts than those caused solely by human presence. Photographic flashes did not cause changes in gross ocular and retinal anatomy of seahorses and did not alter feeding success. Physical manipulation of animals by photographing scuba divers, however, elicited strong stress responses.  

A potential explanation as to why flash has no negative impact is the ripple effect caused by sunlight focusing through waves or wavelets on a sunny day. These bands of light are of a very short duration, but very high intensity (up to 100 times stronger than without the ripple effect). Fish living in such conditions would have evolved to deal with such rapidly changing light conditions. 

The Curtin University team found that frogfish, seahorses and pipefish who were repeatedly gently prodded into position caused them to move far more, usually to escape the errant muck stick. This has drastic implications for the subjects – not only does it stress the fish but may cause it to leave a prime hunting spot, resulting in malnutrition, or to leave a prime hiding spot, its only defense against predation. 

We investigated the pathomorphological and behavioural impacts of photographer behaviour and photographic flashes on 14 benthic fish species that are important for scuba diving tourism and aquarium displays. We ran a field study to test effects of photography on fish behaviour, and two laboratory studies that tested effects of photographic flashes on seahorse behaviour, and ocular and retinal anatomy. 

An important caveat to this experiment: the underwater strobes we used were much stronger than the flashes of normal cameras or phones. The strobes were used at maximum strength, which is not usually done while photographing small animals at close range. So our results represent a worst-case scenario that is unlikely to happen in the real world. 

Does underwater flash photography affect the behaviour, movement and site persistence of seahorses? Harasti, Gladstone, Research paper published on October 2013

The effect of flash photography on seahorse species has never been tested. An experiment was established to test the effect of flash photography and the handling of Hippocampus whitei, a medium-sized seahorse species endemic to Australia, on their behavioural responses, movements and site persistence. A total of 24 H. whitei were utilized in the experiment with eight in each of the three treatments (flash photography, handling and control). The effect of underwater flash photography on H. whitei movements was not significant; however, the effect of handling H. whitei to take a photograph had a significant effect on their short-term behavioural responses to the photographer. Kaplan-Meier log-rank test revealed that there was no significant difference in site persistence of H. whitei from each of the three treatments and that flash photography had no long-term effects on their site persistence. It is concluded that the use of flash photography by divers is a safe and viable technique with H. whitei.

Does Flash Photography Hurt Marine Life? Article published on April 2023

Even repeated flash photography does not seem to cause any kind of permanent retinal damage, at least to shallow-water species that divers are most likely to encounter and photograph whose eyes are used to light. 

Seahorses, for example, are stressed out by scuba divers taking their photos with flash photography. However, the effect is negligible and temporary … unless those divers physically grab the seahorse to move it for a better shot, which is a rant for another time. However, when photographing smaller fish like seahorses, divers get very close to the animal, which itself causes a great deal of stress. Other species of fishes are temporarily “dazzled” by the bright flash of light, leaving them less able to defend themselves from predators. 

By the way, what are the signs of distress?

For frogfish: erecting fins and yawning

For Seahorses (Do not pursue seahorses if they swim away)

• A seahorse will rise up into the water column above the seabed or into surrounding area and swim with its tail curled up;

• A seahorse will hold its head in a downward, chest hugging posture;

• A seahorse will turn its back, curl up, lie flat or move away.

• Seahorse’s colouring will darken, especially in the squares amongst the body ridges;

• The pupils in the eyes of the seahorse will dilate/fluctuate.