Extensive immigration from compensatory hatchery releases into wild Atlantic salmon population in the Baltic sea: spatio-temporal analysis over 18 years

Abstract

Genetic homogenization has been recognized as a serious threat in an increasing number of species, including many salmonid fishes. We assessed the rate and impact of immigration from the main hatchery stocks of Atlantic salmon in the Gulf of Bothnia into one of the largest wild salmon populations in the Baltic Sea, the River Vindelä lven, within a temporal framework of 18 years (from 1985-2003). We provide genetic evidence based on mtDNA and microsatellite markers, using mixed-stock analysis, that a large proportion (66%) of fin-damaged spawners (n ¼ 181) caught in the Ume/ Vindelä lven during 1997-2003 originated from the hatcheries in the Rivers Å ngermanä lven, Luleä lven and Ljusnan. The maximum-likelihood estimate of immigration rate from these hatcheries into the wild Vindelä lven population was 0.068 (95% CI 0.021-0.128) over the studied time period (1985)(1986)(1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003) and reached up to a quarter (m ¼ 0.249, 95% CI 0.106-0.419) of the total population during 1993-2000. This resulted in significant (Po0.01) genetic homogenization trend between the wild Vindelä lven population and hatchery stocks of the Å ngermanä lven and Luleä lven. Our results demonstrate extensive straying from geographically distant hatchery releases into wild salmon population and emphasize the genetic risks associated with current large-scale stocking practices in the Baltic Sea. Heredity (2005) 95, 76-83.

Diversidade genética de pacu do Rio Paranapanema e do estoque de um programa de repovoamento

“…Produzir peixes jovens com alta variabilidade genética não depende apenas de um estoque de reprodutores com esta característica. O inadequado manejo reprodutivo pode promover diminuição da variabilidade genética (Moreira et al, 2007), e em apenas uma geração (Wasko et al, 2004;Porta et al, 2006). A endogamia, a utilização de um pequeno número de reprodutores e a seleção não intencional durante a reprodução (escolha de reprodutores sem pretensões de melhoramento genético, como por exemplo, peixes maiores ou menores e a não utilização de todo o período reprodutivo) são os principais fatores do manejo reprodutivo, que promovem a diminuição da variabilidade genética.…”

“…Neste contexto, o monitoramento genético desses programas é essencial para a conservação genética. Marcadores moleculares são instrumentos eficientes para este propósito (Sekino et al, 2002;Ortega-Villaizán Romo et al, 2006), e para auxiliar no manejo genético nas pisciculturas de forma a minimizar a endogamia e maximizar a variabilidade genética (Wasko et al, 2004).…”

Microsatellite analysis of pacu broodstocks used in the stocking program of Paranapanema River, Brazil

“…Nonetheless, the enhancing programs may have less survival of juveniles and, consequently, the populations in the wild will be permanently affected. The analysis of the genetic differences between the captive broodstocks and populations in the wild is also very important because every one has specific genes for local adaptability, and consequently the survival of juveniles will be affected (Sønstebø et al, 2007;Vasemägi et al, 2005).…”

Impact of climate change and human-mediated introgression on southern European Atlantic salmon populations

“…Human intervention (stocking) is known to have reduced population structuring in other species, for example, partridge (Chen et al, 2006), chukar (Barbanera et al, 2007) and many others (Laikre et al, 2006). In Atlantic salmon, hatchery releases may threaten genetic integrity of even geographically distant wild salmon populations (Vasemägi et al, 2005). The escape or deliberate introduction of captive bred animals into the wild can substantially depress natural recruitment and more specifically can disrupt the capacity of natural populations to adapt to higher winter water temperatures associated with climate variability (McGinnity et al, 2009).…”