Mud shrimps Upogebia pugettensis inhabit U- or Y-shaped burrows on intertidal mud- and sand-flats.  The burrows may extend to depths of 90cm, with sturdy walls consisting of sediment particles and other debris cemented together with mucus secreted by the shrimp.  Mud-shrimp burrows are not usually associated with a sediment mound (unlike ghost shrimps).  Swinbanks & Murray 1981 Sedimentol 28: 201; Swinbanks & Luternauer 1987 J Paleont 61: 315; Griffis & Suchanek 1991 Mar Ecol Progr Ser 79: 171.



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What effects do the activities of mud shrimps Upogegia pugettensis have on other mudflat macrofauna?  This is tested in Willapa Bay, Washington where mud shrimps are excluded from experimental arenas in areas where they are otherwise abundant.  Let’s repeat one set of experiments here.  First, we bury several 20-liter plastic tubs to the level of their rims in the mudflat.  We then fill the tubs with nearby sediment after screening it to remove all macrofauna.  To half the buckets we add 7 large (5-7cm) mud shrimps (Addition), and leave the other half shrimp-free (Exclusion).  A wire-mesh cage is placed on all the buckets for 48h to prevent access by predatory birds and fishes while the shrimps burrow into the sediment.  We then remove the cages and leave the buckets for 1yr.  After this time, and after a second (replicate) year, we sift out the macrofauna from several replicate areas (each 1/200 sq m) in each bucket and assess what effects on macrofaunal abundance the shrimps have had.  The sets of results for the 2 years are similar, so we combine them into grand means (see histograms). 

Results show, firstly, that overall numbers of macrofauna (mainly sedentary tube-dwelling worms and crustaceans) are greater in the Exclusion tubs where mud shrimps are absent than in the Addition tubs.  Finer analysis shows that 4 species (2 polychaetes and 2 crustaceans, indicated in blue with asterisks), all sedentary tube-dwelling forms, are significantly more abundant in the absence of mud shrimps than in their presence.  Abundances of several other species, including the bivalve Macoma balthica, are not significantly affected.  Only one species, a tube-dwelling polychaete (Heteromastus filiformis), is significantly more abundant in the presence of mud shrimps than in their absence.  We conclude that mud shrimps have a significant negative impact on the mudflat macrofauna, likely owing to their large-scale digging and smothering activities.  Posey et al. 1991 J Exper Mar Biol Ecol 148: 283.

NOTE the tubs have mesh screens installed on the sides to aid in water circulation. 

Burrowing activities of mud shrimps and, to a lesser extent of ghost shrimps, seriously interfere with bottom-culture of oysters – so much so, in fact, that since 1963 in Washington oyster-growers have been seasonally treating their oyster beds with a shrimp-killing toxin carbaryl.  Unfortunately, the toxin also kills other arthropods, including crabs, shrimps, and amphipods, as well as juvenile and sub-adult Dungeness crabs Cancer magister, and certain fishes such as English sole.  Use of carbaryl is opposed by crab-fishers, and has been banned in Oregon since 1984.  Dumbauld et al. 1997 J Shellf Res 16: 503; Feldman et al. 2000 Estuaries 23: 141; Dumbauld et al. 2001 Mar Pollut Bull 42: 826; for a review of the environmental ethics of use of carbaryl for controlling ghost- and mud-shrimp populations in Washington state see Feldman et al. 2000 Estuaries 23 (2): 141.

NOTE  in Willapa Bay, Washington where 50% of the state’s oyster production occurs, about 95% of oysters are cultured directly on intertidal mudflats.  Dumbauld et al. 2001 Mar Pollut Bull 42: 826.

NOTE  a non-persistent organocarbamate pesticide (1-napthyl n-methyl carbamate) that is extremely toxic to arthropods (e.g., insects).  Its effect is to inhibit the activity of acetylcholinesterase, which itself functions to inactivate the neurotransmitter acetylcholine.  Death results from muscular and respiratory paralysis.  Carbaryl is applied in powder form during low tides in summer. It is not known whether the practise still exists in Washington

Is there an alternative to application of toxins to control the smothering activities of mud and ghost shrimps on oyster beds?  For example, might the presence of a dense layer of oyster shells (cultch) on top of the mud prevent settlement of the shrimps? Tests on mudflats bearing pavement layers of oyster shells (10-15cm thick) give a mixed answer:  'yes' for ghost shrimps, as settlement is much reduced, and 'no' for mud shrimps, as settlement is little affected.  The authors remark that such a pavement layer would greatly modify the ecology of the mudflat biota beneath, interfere with later harvest of the oysters, offer substratum for oyster spat-eating crabs, possibly turn ghost-shrimp beds into mud-shrimp beds and, by promoting large-scale natural settlement of oyster spat, perhaps ultimately convert the shell pavement into an oyster reef.  Feldman et al. 2000 Estuaries 23: 141.

NOTE cultch is used by oyster culturists routinely as a method to induce settlement of oyster larvae

NOTE the authors provide an excellent and comrehensive review of the past history of oyster culturing in Willapa Bay, Washington, use of toxins to control thalassinid shrimps, and the ecological ramifications of control procedures

The effectiveness of carbaryl in eliminating both mud and ghost shrimps in Willapa Bay, Washington is shown in these graphs.  The data show burrow counts monitored over a 3-yr period after a single application of the toxin as compared with untreated CONTROL plots.  Both species are acutely affected, with numbers decreasing significantly by over 95% within 1-2mo.   The major difference in effect on the 2 species is that numbers of Upogebia remain low for at least 3yr after treatment, while numbers of Neotrypaea rebound after a year. Other parts of the study show high mortality of amphipods associated with application of the toxin, but little or no effect on polychaetes or molluscs.  Dumbauld et al. 2001 Mar Pollut Bull 42: 826.

NOTE  treated with carbaryl at 5.6 kg per hectare in July (Day 0 on the graphs)

NOTE  numbers of the bivalve Cryptomya californica decrease significantly, probably owing to loss of the shrimp burrows in which they live