Factors Influencing Brook Trout (Salvelinus frontinalis) Egg Survival and Development in Streams Influenced by Agriculture

Abstract

Abstract:Increased sedimentation in surface waters due to anthropogenic activities can lead to the deterioration of salmonid spawning habitat through infiltration of excessive fine sediment into redds. This study assessed the effects of sediment on salmonid reproductive habitat on Prince Edward Island, Canada by evaluating egg survival and fry length using brook trout egg in situ incubations. In-stream egg incubators were buried in the substrate of streams in three watersheds with between 10 and 69% agricultural land-use during 2012-2013 and 2013-2014. Accumulated incubator sediment load and associated particle size, incubator organic matter and stream parameters temperature, velocity, bed sediment and particle size were measured over the period of study. There was no significant difference in embryo survival among watersheds. Survival was not related to fine sediment; instead, it increased with higher average temperature that was in turn associated with the presence of groundwater upwelling in the stream. The size of the fry was also not significantly different between watersheds with varying agricultural activity. Fry length was most strongly related to sediment organic matter content. Brook trout are widespread in PEI rivers, including in many rivers that have high sediment loads due to intensive agricultural land use. This species may avoid the adverse effect of fine sediment through their natural adaptation of using groundwater upwelling for spawning. Sedimentation is of particular concern on PEI because of its potential to impact spawning habitat for native salmonids, namely brook trout and Atlantic salmon (Merz et al., 2004;Curry and MacNeill, 2004). While brook trout remain widespread on PEI, Atlantic salmon is only present in about one third of its former rivers (Cairns and MacFarlane, 2015) and its decline has been attributed to a variety of factors, including excessive sedimentation (Guignion et al., 2010). In contrast to the situation on PEI, there is evidence of the decline of brook trout in other parts of the world that has been attributed to landscape alteration (Stranko et al., 2008). Thus, the study of the impacts of sedimentation on brook trout spawning can provide some insight into the persistence of this species on PEI despite the seemingly adverse conditions. The objective of this study was to assess the effects of deposited sediment on brook trout survivorship and fry length on PEI. This study tested the hypothesis that sediment is a limiting factor in salmonid egg survival to hatching and emergence. Survival was assessed by placing in-stream egg incubators in three watersheds with varying degrees of agricultural land-use during two separate spawning seasons. Eggs were monitored for hatching and swimup over the early spring months and the relationship between survival and fine sediment accumulated within the incubators was assessed. Keywords Materials and Methods Study sitesThree rivers on PEI with varying degrees of agricultural landuse within the watershed were selected for the study: Whe...

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