The effects of stream substratum composition on the emergence of salmonid fry

Abstract

Sternecker K, Geist J. The effects of stream substratum composition on the emergence of salmonid fry. Ecology of Freshwater Fish 2010: 19: 537–544. © 2010 John Wiley & Sons A/S Abstract – Salmonid fishes are target species for the conservation of freshwater habitats, but their natural reproduction is often insufficient. The emergence of fry is a crucial phase in the life cycle of salmonids and the stream substratum is the key habitat which regulates the emergence success. In this study, brown trout (Salmo trutta) and Danube salmon (Hucho hucho) eggs were exposed to different sediment textures and the emergence and the postemergence survival and growth were observed under constant water chemical conditions in the laboratory. In both species, textural effects on emergence rate, chronology of emergence, survival rate after emergence and growth after emergence were detected. Fine‐textured substratum (5–8 mm) formed a physical barrier to the posthatch migration of salmonids from the interstitial zone to the open water. The time period between the first and the last emerged fish was shorter in treatments with fine texture compared with coarse substratum. The survival rate was higher in treatments of coarser sediment. The effects of different textures on the growth of fry after emergence differed between brown trout and Danube salmon, which can be explained by different life history strategies. These results suggest that physical characteristics of substratum texture can have strong effects on salmonid emergence, and ultimately on the persistence of salmonid populations. They also suggest that biodiversity conservation in stream ecosystems can greatly benefit from an inclusion of the physical characteristics of the stream bed into catchment‐based management plans.

The importance of stream interstitial conditions for the early‐life‐stage development of the European nase (Chondrostoma nasus L.)

“…Generally, eggs deposited at the surface are likely more vulnerable to predation by other fish species, invertebrates or waterfowl (Dedual, 1990;Keckeis et al, 1996;Persat & Olivier, 1995). If this was the case, then eggs in the interstitial would likely be negatively impacted by high sedimentation rates as reported for other species (Geist & Auerswald, 2007;Marty, Beall, & Parot, 1986;Sternecker & Geist, 2010), low levels of oxygen (Keckeis et al, 1996) and sediment shear stress (Hauer, Unfer, Schmutz, & Habersack, 2007). If this was the case, then eggs in the interstitial would likely be negatively impacted by high sedimentation rates as reported for other species (Geist & Auerswald, 2007;Marty, Beall, & Parot, 1986;Sternecker & Geist, 2010), low levels of oxygen (Keckeis et al, 1996) and sediment shear stress (Hauer, Unfer, Schmutz, & Habersack, 2007).…”

“…To date, research on the effects of fine sediments on fish has been concentrated on species of relatively few families, notably salmonids (Kemp, Sear, Collins, Naden, & Jones, 2011;Sternecker et al, 2013). This might also be of evolutionary relevance, as found for the Danube salmon (Hucho hucho L.) and the brown trout (Salmo trutta L.) (Sternecker, Denic, & Geist, 2014;Sternecker & Geist, 2010). This might also be of evolutionary relevance, as found for the Danube salmon (Hucho hucho L.) and the brown trout (Salmo trutta L.) (Sternecker, Denic, & Geist, 2014;Sternecker & Geist, 2010).…”

Substrate composition determines emergence success and development of European nase larvae (Chondrostoma nasus L.)

“…This is of even greater importance as populations are in a steep decline in their whole distribution area (Peňáz, 1996) and, especially in Bavaria (Germany), where this trend has not yet stopped . Analogously to salmonid species (Sternecker & Geist, 2010), we hypothesised that substrate composition affects the (a) survival and the emergence rate, (b) the timing of emergence and (c) the larval length at emergence. Therefore, this study focuses on a crucial bottleneck in the life cycle of nase, by analysing the effects of different sediment compositions on eggs and larvae under standardised conditions in experimental flumes in a laboratory.…”

Model-Based Evaluation of the Effects of River Discharge Modulations on Physical Fish Habitat Quality

“…The quality and quantity of those remained very low for all of the flow velocities and depth variations that were investigated, and no significant variations were found between the scenarios, suggesting that substratum may be the triggering variable for these habitats. The sediment is very important for spawning, since all of the investigated species lay their eggs into or onto the freshly deposited substratum, or even dig redds for oviposition (as with Hucho hucho) [50,56,66,76,78,79]. The absence of fine sediments, excessive biofilms, and other organic matter is crucial to the survival of the eggs and early juvenile stages.…”

“…The European huchen occurs at a very low density in the Isar in Munich and its tributaries, with fewer than five fishes per 100 m of river [51,52]. Three habitat types that are related to different life cycle stages have been identified [66,67,[70][71][72][73][74][75][76] and were labeled HHA (Habitat for Adults), HHR (Habitat for Adults during the pre-reproduction period), and HHJS (Habitat for spawning and Juveniles) in this study (Table 1).…”