Études de cas sur la gestion
Acambay valley (Central Mexico)
Acambay is located in El Estado de Mexico 169 km northwest of Mexico City in the Alto Lerma zone on the Mexican volcanic belt (altitude 2550 m) in central west Mexico. Acambay is in a valley in the basin of the Lerma river. Although these ponds are closely related to human activities they are of high conservation value because of their high density of endemic species, including axolotl (Ambystoma mexicanum), crayfish (Cambarellus montezumae) and long-finned amarillo (Girardinichthys multiradiatus) (Espinoza et al. 1993, in Zambrano et al. 1999). The annual average annual temperature is 14.2C (maximum 16.8C, minimum 10.6C) (García 1988, in Zambrano et al. 1999).
The Trent is the third longest river in the UK (274 km), and has a catchment area (10 500 km2) that is similar in size to those of the rivers Severn and Thames, while the Ouse is 200 km long (catchment 10 000 km2) and the Avon 180 km long (catchment 3000 km2). The Avon is a major tributary of the River Severn, which discharges into the Bristol Channel, and has a less diverse natural fish fauna than the Trent (Nunn et al. 2007).
In 1996 a cyprinid removal programme commenced at Botany Wetlands with the objective of managing the invasive species, increasing fish diversity, reducing cyanobacterial blooms and hence enhancing the aquatic habitat. Using electrofishing and gill netting, 4073 carp and 261 goldfish, amounting to 10 117 kg of cyprinid biomass were removed between 1996 and 2004 (Pinto et al. 2005). There has been a remarkable improvement in the aquatic habitat of Botany Wetlands since the commencement of the carp removal project; water transparency has increased and the frequency and duration of the cyanobacterial blooms has decreased (Pinto et al. 2005). The success of the programme was monitored by assessing four indicators related to carp populations and two related to habitat; the former included the pattern of length-frequency distribution, mean weight per size class, condition factor (CF) and the catch per unit effort (CPUE), and the latter the Secchi disc transparency and cyanobacterial counts (Pinto et al. 2005). After 8 yr of removal, the plots of carp length–frequency distribution flattened, CF decreased from 2.86 to 1.82 and CPUE decreased from 97 kg day-1 to 50 kg day-1 (Pinto et al. 2005). A 10-fold decrease occurred in cyanobacterial counts and the Secchi disc transparency increased by 20% (Pinto et al. 2005).
Carp removal is only one aspect of wetland rehabilitation at Botany Wetlands, and it needs to be integrated into a comprehensive management scheme for the entire wetland that takes into account the macrophyte community, noxious weeds, water and sediment quality (Pinto et al. 2005). As part of the wetland restoration more than 20 000 fingerlings of native Australian bass Macquaria novemaculeata have been introduced to the wetlands, increasing the potential for juvenile carp predation and biodiversity (Pinto et al. 2005). It is suggested that an environment with clear water dominated by macrophytes should be the target for Botany Wetlands (Pinto et al. 2005).
Lake Naivasha is a freshwater lake, approximately 160 km2 in area, situated in the eastern Kenyan Rift Valley. It is shallow, bordered by papyrus, Cyperus papyrus L., and its aquatic macrophytes are in a state of flux (Adams et al. 2002, in Hickley et al. 2004). It is located 190 km south of the equator at an elevation of 1890 meters above sea level (Britton et al. 2007). Although it became a Ramsar site in 1995 (Wetlands International 2003, in Britton et al. 2007), considerable pressures remain on its ecosystem, with habitat degradation and major fluctuations in water level resulting from climatic factors, anthropogenic activities and the adverse impacts of alien species introductions (Harper & Mavuti 2004, in Britton et al. 2007).
Lake Pamvotis is a tertiary natural shallow lake located in the NW of Greece. Lake Pamvotis has recently been recognised as globally significant for its biodiversity (Krystefek & Reed 2004, in Leonardos et al. 2008) and, because of its great nature conservation value, is now listed in Natura Special Conservation areas under the Habitats Directive EC92 / 43. For biogeographical reasons, it historically contained only four fish species: two endemics (Phoxinellus epiroticus, Squalius pamvoticus), one native to the West Greece (Barbus albanicus) and the ubiquitous Anguilla anguilla. During the last three decades the fish fauna of the lake has shifted from the native, clearwater species to a predominance of introduced species, mainly those adapted for turbid eutrophic water: trichonis roach (Rutilus panosi), C. carpio and Prussian carp (Carassius gibelio), and several Asian cyprinids. The current fish assemblage in the lake is dominated by introduced species particularly the mosquitofish (Gambusia affinis) and the Lourogobios (Economidichthys pygmaeus) in the littoral zone, the benthopelagic allogynogenetic Prussian carp and the opportunistic trichonis roach in the pelagic zone (Leonardos et al. 2008).
Barriers in the form of ‘fish screens’ have been used in Tasmania to attempt to prevent the spread of carp from Lake Sorell and Lake Crescent. The success of these screens has not been determined but carp have not spread to date (W. Fulton, Tasmanian Inland Fisheries Commission, pers. comm. 1998, in Koehn Brumley & Gehrke 2000).
Research by Miller and Provenza 2007 was aimed was to understanding the mechanism of resistance of macrophytes to the common carp and thereby to offer managers a suitable suite of plants to be used in restoring the habitats of Utah Lake and other areas with invasive carp.
This lake belongs to the Dalmatian division, the most specific of all the Euro-Mediterranean subregions because of its five endemic genera and many endemic species (Economidis and Banarescu 1991, in Treer et al. 2003). Prior to carp stocking, the most numerous fish in the lake were eel (Anguilla anguilla) and gray mullet (Mugil cephalus) (Morovic 1964, in Treer et al. 2003).
Leigh Creek coal mine
Efforts have been made to poison this population twice, however both have failed (Beat Odermatt pers. comm. In Unmack, 2003).
Marlborough Region (South Island)
Currently, attempts to eradicate some populations in small ponds are being undertaken.
Murray-Darling BasinWe are experiencing technical difficulties and unable to complete your request. Please try later.
The reported abundance of native fish species in the Murray-Darling Basin has declined over the last century (Harris & Gehrke 1997, Reid et al. 1997, in Nicol et al. 2004) with some species now locally extinct in parts of their distribution (Cadwallader & Gooley 1984, in Nicol et al. 2004). In contrast, carp have undergone a rapid expansion in range and abundance throughout this region since their introduction in the 1960s (Koehn et al. 2000a, in Nicol et al. 2004). Most rivers in the Murray-Darling Basin are severely modified and are typified by degraded native fish populations and abundant carp populations (MDBC 2002, in Nicol et al. 2004).The overwhelming opinion presented in the literature links the invasion by carp with habitat alteration associated with the regulation of rivers within the Murray-Darling Basin for agricultural, industrial, and domestic purposes (Gehrke et al. 1995, Koehn et al. 2000a, MDBC 2002, in Nicol et al. 2004).
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