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.

Holidays and Hemimysis

Cluster of Hemimysis anomala.

Holidays are a great time to relax with friends and enjoy a meal that students rarely have a chance to eat..one with all the food groups. Over the several Thanksgiving dinners I enjoyed this weekend, I tried to think of what I should write about for this entry. After explaining my thesis to family and friends for the third time, the light bulb went on and my search ended.

Here is a quick review of my thesis on the most recent aquatic invasive species, Hemimysis anomala in the Laurentian Great Lakes basin:

Hemimysis are a nearshore freshwater shrimp species native to the Ponto-Caspian region. They are omnivorous diel migrants, which are strongly associated with structure (rocks/cobble, Dreissena shells, piers, etc.). During the day, individuals aggregate into swarms with densities of up to 1800 individuals/m3.

Researchers suspect Hemimysis gained access to the Great Lakes basin by stowing away on transatlantic ships via ballast water (Ricciardi 2007). Hemimysis were first detected in 2006 in both Lake Michigan and Lake Ontario (Pothoven et al., 2007). Since then, their distribution and densities have increased dramatically in the Great Lakes basin (Marty et al., 2009).

Distribution of Hemimysis anomala in the Great Lakes Basin (Marty et al., 2009).

Suspected impact
Hemimysis were intentionally introduced to some European waterways resulting in the decline of phytoplankton and zooplankton biomass (Ketelaars et al. 1999, Borcherding et al. 2006), which reduced available energy to the higher trophic levels. However, some of these lakes found Perca sp. to be voracious predators of Hemimysis (80% of stomachs containing, 75% full of Hemimysis) (Ketelaars et al. 1999).

Yellow Perch: found to consume H. anomala

In North America, a study examining stomachs of nine fish species in Lake Ontario found yellow perch (P. flavescens), rock bass (A. rupestris) and alewife (A. pseudoharengus), had consumed Hemimysis (Lantry et al. 2010).  Of the stomachs analyzed in this study, Hemimysis were present in 83%, 19% and 9% of alewife (n=112), yellow perch (n=63) and rock bass (n=23) respectively (Lantry et al. 2010).






Alewife: found to consume H. anomala.



It is hard to base conclusions strictly on the results of diet analyses as they only offer a snapshot of fish consumption. Diet analysis is a great initial step in determining the impact of a food web disruptor such as a new invasive species. However, using stable isotopes (d13C, d15N) in conjunction with diet analysis will aid in providing a more holistic perspective of the foodweb and discover potential trophic shifts resulting from the invasion of Hemimysis.



Rock bass: found to consume H. anomala.

My thesis has two objectives: 1) Quantify the dominant trophic linkages from invertebrates to fish across a gradient of Hemimysis density (H1: Local fish will consume Hemimysis over other invertebrate prey, H2: Consumption of Hemimysis will cause an enrichment of both d15N and d13C) and 2) Determine nutritional and physiological properties and transfer efficiencies for dominant food web linkages across the same Hemimysis density gradient (H1: Consumption of Hemimysis will result in increases in fish growth rates and condition).

References:

Borcherding, J., Murawski, S., and Arndt, H. 2006. Pupulation ecology, vertical migration and feeding of the Ponto-Caspian invader Hemimysis anomala in a gravel-pit lake connected to the River Rhine. Freshwater Biology 51:2376-2387.

Ketelaars, H.A.M., Lambregts-van de Clundert, F.E., Carpentier, C.J., Wagenvoort, A.J., and Hoogenboezem, W. 1999. Ecological effects of the mass occurrence of the Ponto-Caspian invader, Hemimysis anomala G.O. Sars, 1907 (Crustacea: Mysidacea), in a freshwater storage reservoir in the Netherlands, with notes on its autecology and new records. Hydrobiologia 394: 233-248.


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


Marty, J., Bowen, K., Koops, M.A., Power, M. 2009. Distribution and ecology of Hemimysis anomala, the latest invader of the Great Lakes basin. Hydrobiologia 647(1): 71-80.

Pothoven, S.A., Grigorovich, I.A., Fahenstiel, G.L., and Balcer, M.D. 2007. Introduction of the Ponto-Caspian bloody-red myseid Hemimysis anomala into the Lake Michigan basin. Journal of Great Lakes Research 33: 285-292.

Ricciardi, A. 2007. Forecasting the impacts of Hemimysis anomala: the newest invader discovered in the Great Lakes. Aquatic Invaders 18:1-7.