Regional variation in energy storage strategies in American glass eels from Eastern Canada

Abstract

Energy status was analyzed in glass eels captured during two early waves of arrival at the mouths of the Mersey River, Nova Scotia, Canada (MR), and Grande-Rivière-Blanche, Québec, Canada (GRB), and according to their salinity preference (freshwater, brackish, or saltwater). Glass eels captured in the GRB estuary were larger, more pigmented, and exhibited higher whole-body glycogen, phospholipid, and sterol and wax ester contents. Those from MR had a higher condition index and a higher whole-body triacylglycerol content, suggesting different patterns of storage and/or use of energy reserves. Within a river, a delay of two weeks in estuarine arrival was characterized by significantly lower energy reserves. No differences in energy storage were observed according to salinity preference. Thus, the results revealed the occurrence of different energy storage strategies according to glass eel migration distance and duration, but not according to salinity preference.

River‐Specific Gene Expression Patterns Associated with Habitat Selection for Key Hormone‐Coding Genes in Glass Eel‐Stage American Eels

“…These results, coupled with those demonstrating the absence of differences related to energy storage status according to salinity preference and the presence of strong differences between glass eels of differing origins at the gene expression and cellular levels (Gaillard et al. , ), confirm that the “hypothetical endocrine mechanism for the control of glass eel migratory plasticity” suggested for glass eel‐stage European Eels (Edeline et al. ) does not apply to American Eels.…”

“…As demonstrated by Gaillard et al. (), K n is both a condition index and an indicator of triacylglycerol and glycogen content. Because Gaillard et al.…”

“…The Le Cren condition index ( K n ) was calculated as described by Gaillard et al. (). Linear regressions of log 10 transformed length and wet mass were conducted using data from all individuals that expressed a salinity preference.…”

“…Because Gaillard et al. () already showed that K n , wet mass, length, and pigmentation stage did not differ according to salinity preference, only the presence of a river effect was tested for these variables.…”

“…We studied gene expression tools, an approach that was successfully used previously both in American Eel glass eels (Gaillard et al. , ) and in embryonic and larval European Eels (Politis et al. ), and we studied glass eels colonizing rivers previously associated with different American Eel ecotypes (Mersey River on the Atlantic coast [BW/SW ecotype]; Rivière‐Saint‐Jean, Gulf of St. Lawrence [FW ecotype]; and Grande‐Rivière‐Blanche, St. Lawrence estuary [FW ecotype]; Pavey et al.…”