Maximum Sizes of Fish in Captivity - an Estimation Tool

As a side project to one that I'm working on to quantify swimming room required by fishes, I looked into the predicted maximum size to which fish will grow in captivity. Many of us use FishBase for their maximum size records, and extrapolate captive size estimates from that data. The problem is two-fold, first their records are for maximum sizes recorded, not normal adult size - and second, I had a strong feeling that many fish do not grow as large in captivity as they can in the wild.

What I did was measure the current size of a group of fish in a public aquarium collection. These fish were selected for the criteria that none of them has grown appreciably in the past two years, and all have been in captivity at least 5 years (the range was 5 to 20 years). Needless to say, this was not a large sample set, but I did find 19 good candidates.

The next step was simple, express the current length of each fish as a percentage of the listed maximum adult size on FishBase. I found the fish in the group had reached their maximum captive size in a range from 45% to 91% of the maximum FishBase size for each species. The average was 66%

So, if people are using the FishBase size to estimate how large a fish will grow in an aquarium, it is likely more accurate to use two thirds of that value as the captive maximum size.

 

Fish name	Length  inches	Max. Size  inches	L:M%
Chelmonops butterflyfish	5	8.7	57.5
Blue devil (Paraplesiops)	11.25	13	86.5
Lionfish, volitans	11.25	15	75.0
French angelfish	9	16	56.3
Puffer - Arothron meleagris	8.5	19	44.7
Lookdown	10	19	52.6
Acanthurus xanthopterus	13.75	27	50.9
Aucheoglanis catfish	19.75	27.5	71.8
Giant Gouramy	21	28	75.0
Asian arowana	23	35	65.7
Pseudodoras catfish	36	39.5	91.1
African tigerfish	21	41	51.2
Shark, epaullete	32.5	42	77.4
Pacu	36	42.5	84.7
Black tip shark	38	78	48.7
Black tip shark	40	78	51.3
Plectranthias inermis	1.75	2.1	83.3
Moonlighter	10.75	18	59.7
Tiger shovelnose catfish	32	45	71.1

                                                                                                Average:  66%

 

Length of 19 long-term captive fishes as a function of the percentage attained of the maximum size for that species listed on FishBase. 

 

 

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Comments

[Jay Hemdal]

I would like to expound a bit on my work on maximum fish sizes in captivity. There seems to be some confusion about the study. Although only 19 fish met the criteria as outlined in the project, fully 2300 fish were analyzed, it is just that 2281 of them did not meet the strict criteria:

"None of them has grown appreciably in the past two years, and all have been in captivity at least 5 years (the range was 5 to 20 years)."

Also, the ONLY conclusion that I drew from this is that the maximum size of fish on FISHBASE tends to run larger than what is seen as a maximum size in captivity - to the extent of it being 66% of that value. Remember that FISHBASE lists the maximum recorded size for a fish - not the normal adult size.

Thanks,

Jay