Effects of salinity on specific gravity and viability of eggs of a North American minnow (Cyprinidae)

Abstract

SUMMARY: The influence of salinity on survival, specific gravity, and size of eggs of the endangered Hybognathus amarus (Rio Grande silvery minnow) was studied to provide insight into factors affecting their potential dispersal and fate. Under low salinity conditions egg specific gravity declined significantly in the first hour after spawning as the perivitelline space of the egg filled with water. Egg specific gravity achieved a minimum value approximately 1 h post-spawning and remained approximately constant until hatching, which occurred near 48 h post-spawning at 20ºC. Specific gravity of the egg depended on the salinity of the water surrounding the egg: hardened eggs changed rapidly in diameter and specific gravity when exposed to water of higher salinity. Size and specific gravity of H. amarus eggs also differed when the eggs were incubated in different groundwater sources. Experiments indicated that calcium chloride saline solution had a greater effect on egg specific gravity and size than did solutions of sodium or potassium chlorides. Survival of H. amarus eggs declined sharply at salinity greater than 3 (practical salinity units, PSU) and was only 5% at a salinity of 8. Habitat restoration to benefit H. amarus should consider the salinity of habitats in which eggs incubate.Keywords: fish egg drift, buoyancy, osmosis, survival, Hybognathus amarus. RESUMEN: EFECTOS DE LA SALINIDAD SOBRE LA GRAVEDAD ESPECÍFICA Y LA VIABILIDAD DE HUEVOS DE UNA CARPA NORTEAMERICANA (CIPRINIDAE). -El efecto de la salinidad sobre la supervivencia, gravedad específica y talla de los huevos del ciprínido puesto en peligro de extinción, Hybognathus amarus, fue estudiado para proporcionar información sobre los factores que afectan la dispersión y el destino de los huevos. Bajo condiciones de salinidad baja la gravedad específica del huevo disminuyó de forma significativa durante la primera hora después de la puesta, a medida que el espacio del perivitelino del huevo se fue llenando de agua. La gravedad específica del huevo alcanzó un valor mínimo 1 hora después de la puesta y quedó aproximadamente constante hasta eclosión, que ocurrió alrededor de 48 horas tras la puesta a 20˚C. La gravedad específica del huevo dependió de la salinidad del agua que le rodeaba. Los huevos con corion endurecido cambiaron rápidamente en diámetro y gravedad específica cuando fueron expuestos a agua de salinidad más alta. El tamaño y la gravedad específica de los huevos de H. amarus también se diferenciaron cuando los huevos fueron incubados en diferentes fuentes de agua subterránea. Los experimentos indicaron que la solución salina del cloruro de calcio tuvo un mayor efecto sobre la gravedad específica del huevo que las soluciones de los cloruros del sodio o del potasio. Expuestos a soluciones de salinidad de más de 3 (PSU), la supervivencia de los huevos de H. amarus disminuyó claramente, bajando a sólo el 5% en la solución de 8. La restauración del hábitat con el objetivo de beneficiar a H. amarus debe considerar la salinidad de los hábitats en los...

The emblematic minnows of the North American Great Plains: A synthesis of threats and conservation opportunities

“… References: 1 Cowley et al. (); 2 Welker and Scarnecchia (); 3 Matthews and Maness (); 4 Ostrand and Wilde (); 5 Echelle, Echelle and Hill (); 6 Bryan et al. (); 7 Lutterschmidt and Hutchison (); 8 Bonner et al.…”

“…Mortality of the three species was 100% at salinities greater than 22‰ (Ostrand & Wilde, ). Increased salinity can cause elevated mortality of Rio Grande silvery minnow eggs by reducing the diameter and increasing the specific gravity of the eggs, thereby changing transport dynamics (Cowley, Alleman, Sallenave, McShane & Shirey, ). Further, Rio Grande silvery minnow eggs remain in suspension longer at higher turbidities than at lower turbidities (Medley & Shirey, ).…”

Movement patterns and dispersal potential of Pecos bluntnose shiner (Notropis simus pecosensis) revealed using otolith microchemistry

“…The second less common pattern was passive dispersal with retention of propagules in the upriver reach where residents remained at or above Highway 70 throughout their lives (18% of the fish captured at or above Highway 70). Cowley et al (2009) suggested that bidirectional dispersal (downriver displacement and upriver movement) was important in the life history of a similar Great Plains river fish (Rio Grande silvery minnow, Hybognathus amarus). The combined return of young-of-year from downriver and retention as residents suggests that the current success of the population relies on eventually securing a large portion of the population through egg retention in the upriver reach.…”

“…The eggs are nonadhesive and semibuoyant, and as long as water velocity is sufficient, the propagules will remain suspended within the water column and drift downriver while development occurs (Platania and Altenbach 1998;Cowley et al 2009). Retention of eggs and fry in slack-water nursery habitat reduces the chances of continued downriver displacement and may be key to successful recruitment into the population (Dudley and Platania 2007;Hoagstrom and Turner 2015).…”

Effect of salinity on egg hatching, yolk sac absorption and larval rearing of Senegalese sole (Solea senegalensis Kaup 1858)

“…blastula cells) was demonstrated in Atlantic herring ( Clupea harengus ) (Holliday & Jones 1965) and plaice ( Pleuronectes platessa ) (Holliday & Jones 1967). Moreover, eggs of the freshwater North American minnow ( Hybognathus amarus , Cyprinidae) adapted their specific gravity and volume to the surrounding salinity, revealing an osmotic flux of water out from the periviteline space into the incubation medium (Cowley et al. 2009).…”