Clownfish decline due to aquarium collecting
Picture by Jenny, Creative Commons.
A recent study has shown that collection for the aquarium trade has negatively impacted wild clownfish populations.The study by Alison Jones and coauthors involved visual surveys for clownfishes on two areas of the Great Barrier Reef with contrasting histories of disturbance.
The authors found that anemone and clownfish numbers were adversely affected by the amount of bleached coral present, with both anemones and clownfishes being absent in bleached and unprotected reefs.
It is thought that “[b]leaching causes the anemones to lose their symbionts after which they may shrink and eventually die due to the temporary loss of photosynthesis.
“The shrinkage, weakening or disappearance of the host anemone can limit the [clownfish] population, the size of the female fishes and the potential for new recruits.
“Additionally, loss of fishes can then affect the survival and growth rate of the anemone.
“This negative cycle of shrinkage as a result of bleaching and subsequent loss of [clownfish] protection followed by further shrinkage may have led to serious declines in the anemone habitat available for new fish recruits and this may have depressed the reproductive success of the remaining fishes.”
The authors also discovered that sites that were closed to fishing and aquarium collecting had more anemones and clownfishes, with the clownfish density being as much as 25 times higher than in sites that were more disturbed and where fishing and aquarium collecting were permitted.
The authors assert that the collection of clownfish for the aquarium trade has had a negative impact on populations: “...the assumption of commercial collectors that removing breeding adult [clownfishes] increases survivorship and growth of young recruits is contentious…
“Removing breeding adults or even sub-adults could cause the anemone to shrink, thereby reducing the amount of space for new recruits, and it may be up to 6 months before the fishes begin to breed again…”
For more information, see the paper: Jones, AM, S Gardner and W Sinclair (2008) - Losing ‘Nemo’: bleaching and collection appear to reduce inshore populations of anemonefishes. Journal of Fish Biology 73, pp. 753–761.
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Heok Hee Ng: 13.8.2008Views: Read 3,152 times
Comments feed
"We'll need to read the whole paper - what's printed above does not distinguish between food fishing and aquarium collection. Also this summary jumps straight from a descriptive of the widespread adverse effects of coral bleaching to numerical differences between open and closed sites.
I agree it's a nonsense that so many of these fish are still imported when the tank bred fish are so much hardier. "
Date: Wednesday August 13th, 2008, 12:08 pm
"The paper is specifically about aquarium collecting, not food, I believe Wayne.
Jones, AM, S Gardner and W Sinclair (2008) - Losing ‘Nemo’: bleaching and collection appear to reduce inshore populations of anemonefishes. Journal of Fish Biology 73, pp. 753–761."
Date: Wednesday August 13th, 2008, 12:29 pm
"The paper is specifically about aquarium collecting. The reason food fish are mentioned because both commercial food fishing and aquarium collecting take place in the permitted fishing areas of the Great Barrier Reef."
Posted by: Heok Hee Ng - 1 year, 3 months agoDate: Wednesday August 13th, 2008, 1:17 pm
"Considering the fact that common clownfish are bred in captivity in large numbers to satisfy demand from fishkeepers I think it's strange that numbers of clownfish are in decline in the wild. Also since wild clownfish don't usually last long in captivity I don't know of anyone who would want to keep them. "
Posted by: Luke Allsop - 1 year, 3 months agoDate: Wednesday August 13th, 2008, 8:40 pm
"Sadly, I think it is likely as a result of their ongoing popularity and short captive life span that so many are wild caught to replace and replenish the casualties of poor housing and stress associated acclimatization problems. Also, I think you'll find that almost everyone in the marine hobby wants to keep clownfishes!
My two pairs are all tank bred hardies - soon I am anticipating flooding my local market with tough black percs and maroons - to do my bit.
We can all try to be responsible firstly, by only buying fish we can successfully accommodate and also by striving to purchase from ethical, MAC certified dealers and those shops which can reliably tell you the exact source of their stock. Making friends and contacts within the hobby helps you avoid having to buy from high - turnover unethical sellers too.
Environmental perturbations such as symbiont bleaching are always magnified as an impact on ecosystems when combined with other anthropogenic impacts such as collection. This is the case particularly as the methodology for capture is rarely based on good population ecology /science and rather, ease of capture or perceptions such as 'removing larger adults will allow replacement of breeding stock from younger life stages.' Rather, it is more the case that removal of those mature individuals within the breeding population causes a significant set back in local clownfish population recovery and continued fecundity; as the article suggests. "
Date: Wednesday October 15th, 2008, 5:13 pm
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 | Singapore-based ichthyologist Dr Heok Hee Ng is a leading expert on Asian catfishes and has described dozens of fish ranging from catfishes, to nandids and cyprinids. |
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"Many of these clowns can be quite easily tank bred, so there is no need to collect wild specimens.
Posted by: Hannah Edwards - 1 year, 3 months agoAnyone who insists on only keeping wild species are just marine 'snobs.'
Let's keep marine fish responsibly. Before it's too late. "
Date: Wednesday August 13th, 2008, 10:01 am