Skip to main content

Comparative suitability of binocular observation, burrow counting and excavation for the quantification of the mangrove fiddler crab Uca annulipes (H. Milne Edwards)

Abstract

Quantification of mangrove crabs is notoriously difficult. Several techniques have been applied in the past, but have rarely been tested. This paper looks at the use of burrow counts (BUR), binocular counts (BIN) and excavation (EX) for quantifying the fiddler crab Uca annulipes (H. Milne Edwards). Fieldwork took place at Maruhubi mangrove (Zanzibar, Tanzania). Twelve 1 m2 quadrats were assessed on one spring cycle and one neap cycle. The results showed a strong correlation between carapace width (CW) and burrow diameter (BD), namely CW (mm) = 1.37BD (mm) −0.64 (r 2=0.98; p<0.001; DF=73). The mean spring tide densities were 77.8 m−2 (EX), 43.3 m−2 (BIN) and 104.8 m−2 (BUR). Of these, 37% (EX), 19% (BIN) and 42% (BUR) were juveniles (<7 mm CW). Census densities did not vary significantly between tides, although total BUR decreased from 1257 (spring) to 949 (neap). Whereas BIN significantly underestimated EX on both tides, BUR only significantly overestimated EX on the spring tide. Overall, burrow quantification matched EX better than binocular counts, suggesting the former is better for the quantification of U. annulipes. Whilst binocular census may be most appropriately carried out on spring tides, burrow quantification may be better on neap tides. A major reason for BIN underestimates and BUR overestimates were discrepancies in juvenile counts. Thus, 28% (spring) to 39% (neap) of adults, but 72% of excavated juveniles were unaccounted for by BIN. Spring tide BUR overestimated excavated adults by 25% but juveniles by 50%. Female BIN matched EX on the spring, but not the neap tide. Male binocular counts were significantly lower than EX on both tides. The potential influences on the results of crab size, sex, emigration and the method of sorting sediment during excavation are discussed.

This is a preview of subscription content, access via your institution.

References

  1. Crane, J., 1975. Fiddler Crabs of the World. Ocypodidae: Genus Uca. Princeton University Press, New Jersey. 736 pp.

    Google Scholar 

  2. Dray, T. & J. Paula, 1998. Ecological aspects of the populations of the crab Dotilla fenestrata (Hilgendorf, 1869) (Brachyura: Ocypodidae), in the tidal flats of Inhaca Island (Mozambique). J. nat. Hist. 32: 1525–1534.

    Google Scholar 

  3. Ekwezor, T. K. E., 1985. A baseline survey for the monitoring of oil pollution in the Bonny Estuary, Nigeria. M.Phil. thesis, Riverstate University of Science and Technology, Port Hacourt, Nigeria. In Snowdon, R. J. & T. K. E Ekwezor (eds), Littoral Infauna of a West African Estuary: An Oil Pollution Baseline Survey. Mar. Biol. 105: 51–57.

    Google Scholar 

  4. Ens, B. J. & M. Klaassen, 1993. Flocking and feeding in the fiddler crab (Uca tangeri): prey availability as risk-taking behaviour. Netherl. J. Sea Res 31: 477–494.

    Google Scholar 

  5. Frith, D. W. & S. Brunenmeister, 1980. Ecological and populations studies of fiddler crabs (Ocypodidae, Genus Uca) on a mangrove shore at Phuket Island, Western Peninsular Thailand. Crustaceana 39: 157–183.

    Google Scholar 

  6. Frusher, S. D., R. L. Giddens & F. J. Smith, 1994. Distribution and abundance of grapsid crabs (Grapsidae) in a mangrove estuary: effects on sediment characteristics, salinity tolerances and osmoregulatory ability. Estuaries 17: 647–654.

    Google Scholar 

  7. Genoni, G. P., 1991. Increased burrowing by fiddler crabs Uca rapax (Smith) (Decapoda: Ocypodidae) in response to low food supply. J. exp. mar. Biol. Ecol. 147: 267–285.

    Google Scholar 

  8. Golley, F., H. T. Odum & R. F. Wilson, 1962. The structure and metabolism of a Puerto Rican red mangrove forest in May. Ecology 43: 9–19.

    Google Scholar 

  9. Hartnoll, R. G., 1975. The Grapsidae and Ocypodidae (Decapoda: Brachyura) of Tanzania. J. Zool. Lond. 177: 305–328.

    Google Scholar 

  10. Hockett, J. C. & H. Kritzler, 1972. Capture-recapture methods with Uca. Biol. Bull. 142: 49–56.

    Google Scholar 

  11. Icely, J. D. & D. A. Jones, 1978. Factors affecting the distribution of the genus Uca (Crustacea: Ocypodidae) on an East African shore. Estuar. coast. mar. Sci. 6: 315–325.

    Google Scholar 

  12. Krebs, C. T. & I. Valiela, 1978. Effect of experimentally applied chlorinated hydrocarbons on the biomass of the fiddler crab, Uca pugnax (Smith). Estuar. coast. mar. Sci. 6: 375–386.

    Google Scholar 

  13. Lee, S. Y., 1998. Ecological role of grapsid crabs in mangrove ecosystems: a review. Mar. Freshwat. Res. 49: 335–343.

    Google Scholar 

  14. Machiwa, J. F., 1998. Distribution and remineralization of organic carbon in sediments of a mangrove stand partly contaminated with sewage waste. Ambio 27: 740–744.

    Google Scholar 

  15. Machiwa, J. F. & R. O. Hallberg, 1995. Flora and crabs in a mangrove forest partly distorted by human activities, Zanzibar. Ambio 24: 492–496.

    Google Scholar 

  16. Macintosh, D. J., 1977. Quantitative sampling and production estimates of fiddler crabs in a Malaysian mangrove. Mar. Res. Indonesia 18: 59.

    Google Scholar 

  17. Macintosh, D. J., 1979. The ecology and energetics of mangrove fiddler crabs (Uca spp.) on the west coast of the Malay Peninsula. Doctoral thesis: University of Malaya.

  18. Macintosh, D. J., 1984. Ecology and productivity of Malaysian mangrove crab populations (Decapoda: Brachyura). Proc. As. Symp. Mangr. Env. – Res. & Manag. 1984: 354–377.

    Google Scholar 

  19. Macintosh, D. J., 1988. The ecology and physiology of decapods of mangrove swamps. In Fincham, A. A. & P. S. Rainbow (eds), Aspects of Decapod Crustacean Biology. Symp. zool. Soc. Lond. No. 59: 315–341.

  20. McIvor, C. C. & T. J. Smith, 1993. Differences in the crab fauna of mangrove areas at a Southwest Florida and a Northeast Australia location; Implications for leaf litter processing. Estuaries 18: 591–597.

    Google Scholar 

  21. MacNae, W., 1968. A general account of the fauna and flora of mangrove swamps and forests in the Indo-West-Pacific region. Adv. mar. Biol. 6: 73–270.

    Google Scholar 

  22. Miller, D. C., 1961. The feeding mechanisms of fiddler crabs, with ecological considerations of feeding adaptations. Zoologica 46: 89–100.

    Google Scholar 

  23. Mouton, E. C. & D. L. Felder, 1996. Burrow distributions and populations estimates for the fiddler crabs Uca spinicarpa and Uca longisignalis in a Gulf of Mexico salt marsh. Estuaries 19: 51–61.

    Google Scholar 

  24. Murai, M., S. Goshima & Y. Nakasone, 1982. Some behavioural characteristics related to food supply and soil texture of burrowing habitats observed on Uca vocans vocans and U.lactea perplexa. Mar. Biol. 66: 191–197.

    Google Scholar 

  25. Murai, M., S. Goshima & Y. Nakasone, 1983. Adaptive droving behaviour observed in the fiddler crab Uca vocans vocans. Mar. Biol. 76: 159–164.

    Google Scholar 

  26. Nakasone, Y. & M. Murai, 1998. Mating behaviour of Uca lactea perplexa (Decapoda:Ocypodidae). J. crust. Biol. 18: 70–77.

    Google Scholar 

  27. Nobbs, M. & McGuinness, 1999. Developing methods for quantifying the apparent abundance of fiddler crabs (Ocypodidae: Uca) in mangrove habitats. Aust. J. Ecol. 24: 43–49.

    Google Scholar 

  28. Olafsson, E. & S.G. M. Ndaro, 1997. Impact of the mangrove crabs Uca annulipes and Dotilla fenestrata on meiobenthos. Mar. Ecol. Progr. Ser. 158: 225–231.

    Google Scholar 

  29. Ono, Y., 1965. On the ecological distribution of ocypodid crabs in the estuary. Mem. Fac. Sci. Kyoshu Univ., Ser. E Biol. 4: 1–60.

    Google Scholar 

  30. Palmer, J. D., 1973. Tidal rhythms: the clock control of the rhythmic physiology of marine organisms. Biol. Rev. 48: 377–418.

    Google Scholar 

  31. Salmon, M., 1984. The courtship, aggression and mating system of a 'primitive' fiddler crab (Uca vocans: Ocypodidae). Trans. Zool. Soc. Lond. 37: 1–50.

    Google Scholar 

  32. Salmon, M., 1987. On the reproductive behaviour of the fiddler crab Uca thayeri, with comparisons to U. pugilator and U. vocans: evidence for behavioural convergence. J. crust. Biol. 7: 25–44.

    Google Scholar 

  33. Salmon, M. & G. W. Hyatt, 1983. Spatial and temporal aspects of reproduction in North Carolina fiddler crabs (Uca pugilator Bosc). J. exp. mar. Biol. Ecol. 70: 21–43.

    Google Scholar 

  34. Sasekumar, A., 1974. Distribution of macrofauna on a Malayan mangrove shore. J. anim. Ecol. 43: 51–69.

    Google Scholar 

  35. Smith, T. J., K. G. Boto, S. D. Frusher & R. L. Giddens, 1991. Keystone species and mangrove forest dynamics: the influence of burrowing by crabs on soil nutrient status and forest productivity. Estuar. coast. mar. Sci. 33: 419–432.

    Google Scholar 

  36. Snowdon, R. J. & T. K. E. Ekwezor, 1990. Littoral infauna of aWest African estuary: an oil pollution baseline survey. Mar. Biol. 105: 51–57.

    Google Scholar 

  37. Teal, J. M., 1958. Distribution of fiddler crabs in Georgia salt marshes. Ecology 39: 185–193.

    Google Scholar 

  38. Valiela, I., D. F. Babiec, W. Atherton, S. Seitzinger & C. Krebs, 1974. Some consequences of sexual dimorphism: feeding in male and female fiddler crabs, Uca pugnax (Smith). Biol. Bull. 147: 652–660.

    Google Scholar 

  39. Weissburg, M., 1992. Functional analysis of fiddler crab foraging: sex-specific mechanics and constraints in Uca pugnax (smith). J. exp. mar. Biol. Ecol. 156: 105–124.

    Google Scholar 

  40. Zucker, N., 1978. Monthly reproductive cycles in three sympatric hood building tropical fiddler crabs (Genus Uca). Biol. Bull. 155: 410–424.

    Google Scholar 

Download references

Author information

Affiliations

Authors

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Skov, M., Hartnoll, R. Comparative suitability of binocular observation, burrow counting and excavation for the quantification of the mangrove fiddler crab Uca annulipes (H. Milne Edwards). Hydrobiologia 449, 201–212 (2001). https://doi.org/10.1023/A:1017598616178

Download citation

  • Uca
  • census techniques
  • mangrove
  • East Africa