Conservation Great raft spider

1 conservation

1.1 united kingdom
1.2 reintroduction
1.3 norway

conservation

cladium reed beds @ redgrave , lopham fen typical of d. plantarius habitat

although species distributed in europe, under-recording , confusion on identification make assessment of status difficult. populations known have declined substantially throughout range particularly in western , central areas remaining populations believed established in scandinavia , baltic states. these reductions in population due degradation , loss of habitat. great raft spider listed vulnerable species on iucn red list.

united kingdom

the great raft spider has been identified @ 3 sites in uk. due extreme rarity listed endangered, protected under schedule 5 of wildlife , countryside act 1981 , provided species action plan in 1999. revised targets published in 2006 reports on targets published in 2002, 2005 , 2008. principal threats species in uk identified water abstraction, inappropriate ditch management, deterioration in water quality , loss of suitable wetland habitat.

original targets aimed to: increase range of population ten-fold , increase population density mean maximum of around 15 individuals per pool @ redgrave , lopham fen. maintain density , range of fen raft spider on pevensey levels , introduce populations 2 suitable new sites 2010. in 2006, these revised to: increase range of spider 13 ha of habitat occupied 3 years in 5 2010 , 65 ha 2020 @ redgrave & lopham fen. prevent overall decrease in range @ pevensey levels @ time levels recorded in 1990 , increase sites sustainable populations 6 2010 , 12 2020.

the spider first found in south wales in 2003 in disused tennant canal @ pant-y-sais fen. surveying found stable population identifying further occurrences @ nearby crymlyn bog , in connecting wetlands full range of spider not known. due difficulty of surveying work in wetland terrain , problems identification. habitat @ site considered enough population not declining.

a survey in 1992 @ pevensey levels estimated population @ on 3000 adult females. population considered stable , conservation efforts @ site have focused on maintaining level. population has been found @ small artificial pond site derived pevensey material. review of pevensy population since last count has been recommended.

redgrave , lopham fen first site in uk @ population of great raft spider recorded. following discovery in 1956 number of new pools dug encourage population expansion. however, water extraction nearby borehole , series of droughts in 1980s reduced population 2 isolated areas on reserve. throughout period irrigation of pools inhabited spider enabled continuation of population. removal of borehole in 1999 expected trigger increase in population water levels returned normal. however, study carried out in 2006 showed no noticeable change had occurred. population of fen raft spider remains small , restricted in distribution stable. recommendations future management of population include increasing depths of turf pool, creating more pool habitats , greater, more focused use of water management in reserve.

reintroduction

in october 2010 first introduction of great raft spider population new site in uk carried out in joint project natural england , suffolk wildlife trust , supported grant bbc wildlife fund. project saw around 3000 spiderlings bred , reared dr. helen smith , john innes centre, 1600 of released suitable dykes @ suffolk wildlife trust castle marshes nature reserve. site part of suffolk broads , lies 50 kilometres (31 mi) downstream, redgrave , lopham fen, between lowestoft , beccles. work carried out improve ditch network @ site prepare reintroduction , provide optimal habitat new spider population.

castle marshes nature reserve, site of first great raft spider reintroduction in uk.

the spiderlings bred adults both redgrave , lopham fen , pevensey levels sub-populations. increase genetic variability of new population , increase chances of survival. each spiderling hand reared in separate test tubes , fed fruit flies. if new population establishes 1 of 4 great raft spider populations in uk. population of spiders introduced @ same time redgrave , lopham fen support small population present.

norway

in july 2013, wildlife enthusiast found suspected specimen in rakkestad, Østfold county in norway. several experts have confirmed descriptions belonging great raft spider. make first confirmed sighting of species within norway.