Modelling the benefits of American Mink Mustela vison management options for terns in west Scotland

American Mink Mustela vison is a semi-aquatic predator that has invaded the west coast of Scotland and many of its associated islands. We developed a GIS model of their potential range based on their dispersal abilities and habitat use, which revealed that most islands in west Scotland are accessible to Mink, and that these host a large proportion of the region's Common Sterna hirundo and Arctic Terns S. paradisaea . Mink are predators on tern eggs and chicks, and statistical modelling of long-term productivity data demonstrated that unprotected sites within their range have an average productivity of 0.33 chicks per pair, whereas that at sites where Mink were trapped was 253% higher. We assessed the benefits of current Mink control projects for terns in the Western Isles and the remainder of west Scotland using a population modelling approach. This showed that both projects delivered considerable benefits for Common Terns, because a large proportion of their numbers were within the area of the control programmes and in sites that would be accessible to Mink if no control were in operation. For Arctic Terns, the benefits were less clear, as a larger proportion of their numbers were outside the control areas, and many of these were in sites isolated from, or unsuitable for, Mink. We discuss the implications of these findings for future strategic planning of Mink management in west Scotland.     

Effect of Graft and Sexual Hybridization on the Nodulation of Trifolium ambiguum M.B.

Trifolium ambiguum M.B. is a potentially important clover species,but it has not been used widely as a forage legume because itnodulates sparsely or not at all and the nodules formed areusually ineffective. In some compatible grafts of T. hybridumon T. ambiguum effective nodules developed on the roots of thestock. In addition, effective nodulation was obtained on thesexual hybrid between these two species. The investigation dealswith the effectiveness of nodulation of the graft and sexualhybrids and also of the two host species when inoculated withisolates from the graft hybrid, the sexual hybrid, T. hybridum,and from effectively nodulating T. ambiguum.     

Crustecdysone Mediated Changes in Crayfish

Molting in crayfish, essential for growth is preceded by a decreasein total organic content during premolt. Mineral, as calcium,is conserved in gastroliths after mobilization from the exoskeleton.Crustecdysone treatment results in gastrolith formation by intactcrayfish in intermolt, state C, but does not influence the rateof gastrolith formation in eyestalkless animals. Moreover, therate of gastrolith formation is not increased at higher hormonedoses; conversely, less dense, abnormal gastrohths result, whileapolysis is evident by 48 to 60 hours after treatment. It appearsthat crustecdysone promotes reabsorption of the organic matrixsince treatment with this hormone does not lead to a measureabledecrease in calcium content of shell based on dry weight. Premolt crayfish normally have a higher amino acid pool in alltissues than do those in intermolt, and eyestalk removal fromintermolt crayfish results in an increase in the free-aminoacid level of all tissues by 24 hours; crustecdysone treatmentresults in a significant increase in muscle amino acids by 12hours after a hormone dose of 5 µg/g body weight. In thecontext of integumentary growth and protein synthesis low dosesof crustecdysone (1 µg/g) increase the in vivo incorporationof amino acid into hypodermis, but not hepatopancreas, by 24hours, and the increase is significant by 36 hours; a higherdose (5 µg) does not change this rate of incorporation.Selective increase in hypodermis protein is not evident in acidphosphatase levels from 12 to 48 hours, but respiration of thistissue is significantly elevated within two hours after hormoneinjection.