Put another shrimp on the barbie

For my thesis, I’m studying the new invasive species Hemimysis anomala. This new invasive has already been incorporated into the Lake Ontario food web. Lantry et al. (2010) published one of the first reported observations of Hemimysis consumption by fish.

They fished gill nets at two locations of known Hemimysis colonization in Lake Ontario. Stomachs were removed from caught fish an examined for the presence of Hemimysis. Three of nine fish species caught consumed Hemimysis.

Table 1. Frequency of occurrence (%) of stomachs containing Hemimysis anomala from fish sampled from gill nets fished during August – October 2007. Sample size (n) refers to the total number of fish stomachs examined including empty stomachs and TL is total length.

Species	Sampling Month	n	Mean TL (mm)	TL range	% Frequency
Alewife	August	53	173.7 (9.7)	152–190	92.4
Alewife	September	49	178.1 (9.9)	150–200	69.6
Alewife	October	10	170.8 (9.7)	157–188	100.0
Rock bass	August	6	166.7 (9.5)	154–179	33.3
Rock bass	September	7	178.3 (35.6)	148–255	0
Rock bass	October	10	188.6 (38.4)	116–275	0
Yellow Perch	September	2	213.5 (13.4)	204–223	0
Yellow Perch	October	61	180.0 (33.9)	110–271	2.0
Smallmouth bass	August	48	233.9 (24.3)	185–279	0
Smallmouth bass	September	6	220.8 (19.0)	193–247	0
Smallmouth bass	October	1	235		0
Round Goby	August	42	141.1 (20.2)	96–177	0
Round Goby	September	7	159.7 (23.2)	135–189	0
Round Goby	October	5	127.6 (31.5)	91–161
Spottail Shiner	October	179	119.0 (4.5)	108–134	0
Gizzard shad	October	9	142.8 (71.9)	89–339	0
White perch	October	4	172.5 (82.8)	88–247	0
Log perch	October	1	129		0

*Above table and caption from Lantry et al. 2010.

Dislikes:

The authors make the assumption that setting nets in 8 m of water will eliminate the possibility of the native mysid from being consumed. However, some fish are very mobile (i.e. alewife) and there is a possibility that fish could have consumed the native mysid species before swimming into the nets. If this was not checked and it was assumed any mysid found in the stomachs were Hemimysis then the estimates may be inflated.

Likes:

This study is one of the first reports of observed fish consumption of Hemimysis. There was also a good discussion surrounding why some species would have higher predation efficiencies on Hemimysis.

Please read and enjoy this article. Formulate your own opinions. This organism has just recently invaded the Great Lakes and it’s impacts on the native ecosystem are still to be determined.

Reference:
Lantry, B.F., Walsh, M.G., Johnson, J.H., McKenna, J.E.Jr. (2010) Occurence of the Great Lake's most recent invader, Hemimysis anomala, in the diet of fishes in southeastern Lake Ontario. Journal of Great Lakes Research 36:179-183.