A protocol for stocking hatchery reared freshwater pearl mussel Margaritifera margaritifera

Abstract

ABSTRACT1. Freshwater pearl mussel (Margaritifera margaritifera L.) populations are under serious threat of extinction throughout their geographical range and only a few remnant populations are recruiting to adulthood. Consequently, M. margaritifera is classified as endangered on the International Union for Conservation of Nature Red List.2. Several institutions across many countries have set up Ark sites at hatcheries to culture and rear young M. margaritifera from population remnants, with the intention of stocking these juveniles into rivers. The release location must fulfill the habitat requirements for the full life-cycle of the species, so they can contribute to the next generation and thus the long-term recovery of the species. However, little research or advice exists about how to decide if river environments are suitable for stocking.3. A protocol is presented for determining whether a M. margaritifera population will benefit from stocking hatchery reared juveniles and how to identify suitable areas. Stocking locations are considered from catchment scale to microscale using water quality (reach), macrohabitat (site) and microhabitat, including physicochemical properties of the substratum (spots).4. A case study of the River Esk in north-east England, is incorporated to exemplify the myriad of considerations surrounding attempts to conserve M. margaritifera, and describes how implementation of the protocol can structure and assist stocking programmes.

Conservation status of the freshwater pearl mussel Margaritifera margaritifera in Portugal

“…On the contrary, and due to their extended life span, if adults can survive in present disturbed conditions, conservation may be possible if the appropriate management measures, that guarantee effective reproduction and future recruitment, are implemented (Hastie, 2011). In the same vein, and due to the high fertility, captive breeding and future stocking in the wild can be a viable solution if the suitable conditions are restored (Preston et al, 2007;Bolland et al, 2010;Thomas et al, 2010;Gum et al, 2011).…”

“…Some successful captive breeding programs for M. margaritifera already exist in Europe, and so, these techniques are already available to be used in Portugal, taking in account the best practices that should include genetic information, careful determination of habitat requirements (from the macro to the microscale) and assessment of suitable food resources (e.g. Preston et al, 2007;Bolland et al, 2010;Gum et al, 2011;Wilson et al, 2012;Eybe et al, 2013;Scheder et al, 2014).…”

An alien fish threatens an endangered parasitic bivalve: the relationship between brook trout (Salvelinus fontinalis) and freshwater pearl mussel (Margaritifera margaritifera) in northern Europe

“…In addition to the salmonid host specificity, the long duration of the parasitic stage and the remarkable growth of glochidia during that stage distinguish FPM from many other mussel species; in the northernmost range of FPM, the glochidia remain attached on the host fish for almost a year, from early autumn to late summer of the following year (Young and Williams 1984b, Hruška 1992, Ieshko et al 2009, Schmidt and Vandré 2010, while in southern latitudes the parasitic life stage may end several months earlier (Cunjak and McGladdery 1991, Eybe et al 2015. Nevertheless, during that stage the glochidia metamorphose into slightly ovoid juvenile mussels of 400-500 μm length (Young and Williams 1984b, Bauer 1987b, 1987c, Bauer and Vogel 1987, Schmidt and Vandré 2010, Denic et al 2015, after which the juveniles leave the host and penetrate into the river bottom substratum for several years (Young and Williams 1983a, Bauer 1988, San Miguel et al 2004, Geist and Auerswald 2007, Bolland et al 2010, Ostrovsky and Popov 2011, presumably to hide from predators (see Zimmerman et al 2003). The mortality of FPM is very high during these early life stages even in optimal conditions; it is estimated that 95-99 % of glochidia shed into the water do not reach a suitable host and die, 90-95 % of the glochidia attached to a suitable host die before completing metamorphosis, and a further 95 % of young mussels are lost between detachment from the host and establishment in the bottom substratum (Young and Williams 1984a, Preston et al 2007, Schmidt and Vandré 2010.…”

“…Many conservation strategies for the restoration of FPM populations have been developed; habitat protection and restoration , Bolland et al 2010, Geist 2010, Horton et al 2015 probably are the primary strategies but methods such as reintroduction of mussels (Young and Williams 1983b, Valovirta 1993, Beasley and Roberts 1999, Bolland et al 2010, Geist 2010, release of glochidia-infected fish (Buddensiek 1995, Geist et al 2006, Thomas et al 2010, Simon et al 2015 and artificial culture of mussels (Buddensiek 1995, Preston et al 2007, Geist 2010, Schmidt and Vandré 2010, Thomas et al 2010, Gum et al 2011, Simon et al 2015 are also widely used. However, despite the conservation activities, increased freshwater mussel research (see e.g.…”

Negotiating river restoration: The role of divergent reframing in environmental decision-making

“…1 This was undertaken as part of a wider ethnographic analysis amongst farmers in the River Esk catchment between 2007and 2010(Emery, 2010.…”