Habitat expansion of the Harris mud crab Rhithropanopeus harrisii (Gould, 1841) in the northern Baltic Sea: potential consequences for the eelgrass food web

Abstract Because fisheries operate within a complex array of species interactions, scientists increasingly recommend multispecies approaches to fisheries management. We created a food web model for the Baltic Sea proper, using the Ecopath with Ecosim software, to evaluate interactions between fisheries and the food web from 1974 to 2000. The model was based largely on values generated by multispecies virtual population analysis (MSVPA). Ecosim outputs closely reproduced MSVPA biomass estimates and catch data for sprat (Sprattus sprattus), herring (Clupea harengus), and cod (Gadus morhua), but only after making adjustments to cod recruitment, to vulnerability to predation of specific species, and to foraging times. Among the necessary adjustments were divergent trophic relationships between cod and clupeids: cod exhibited top-down control on sprat biomass, but had little influence on herring. Fishing, the chief source of mortality for cod and herring, and cod reproduction, as driven by oceanographic conditions as well as unexplained variability, were also key structuring forces. The model generated many hypotheses about relationships between key biota in the Baltic Sea food web and may ultimately provide a basis for estimating community responses to management actions.

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Assessment of Crab Limb Regeneration as an Assay for Developmental Toxicity

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f92-142 ◽

1992 ◽

Vol 49 (6) ◽

pp. 1268-1273 ◽

Cited By ~ 6

Author(s):

Anthony S. Clare ◽

John D. Costlow ◽

Hassan M. Bedair ◽

George Lumb

Keyword(s):

Developmental Toxicity ◽

Limb Regeneration ◽

Optimal Conditions ◽

Mud Crab ◽

Rhithropanopeus Harrisii ◽

Full Size ◽

Juvenile Crab ◽

Sublethal Concentrations ◽

Crab Stage ◽

Duration Of Development

The regeneration of a cheliped that is autotomised at the final larval stage, the megalopa, of the mud crab Rhithropanopeus harrisii (Gould) forms the basis of an assay for developmental toxicity. Cheliped regeneration is followed through to the third juvenile crab stage; a regenerate that is approximately two thirds full size normally emerges at the moult to the second crab, and full size is attained at crab 3. The absence of a regenerate at crab 2, or a regenerate that is smaller than normal and/or malformed, is scored as abnormal regeneration. Other parameters examined in this assay include survival and duration of development. The assay is of comparatively short duration (approximately 2 wk), and survival is high following autotomy under optimal conditions. Four insecticides and a herbicide have been tested in the assay at lethal and sublethal concentrations. Of these compounds, methomyl, carbofuran, and alachlor induced abnormal regeneration whereas cypermethrin and RH 5849 did not affect regeneration at the concentrations tested. Although reproducibility of results needs improvement, crab limb regeneration is otherwise a practical assay for developmental toxicity.

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