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J. B. K. Leonard

Publications and source records attributed to J. B. K. Leonard.

7 recordsLinked to original sources
USGS2005

Changes in haematology during upstream migration to American shad

Heart mass of American shad Alosa sapidissima did not change during migration in the Connecticut River. Spleen mass decreased and there was an increase in available blood haemoglobin (+22%) and haematocrit (+9%). The decreases in spleen somatic index (-29%) and spleen haemoglobin content (-15%) were dependent upon distance travelled upriver and not seasonal migration timing or short-term exercise events such as passage up a fish ladder. There was no effect of migration timing on any of the blood parameters measured, suggesting that any physiological responses during migration were based on distance travelled rather than seasonally variable conditions such as temperature, although blood haemoglobin (+24%) and haematocrit (+21%) increased after passage up a fish ladder. These changes in haematological physiology occurring during upstream migration may increase swimming performance and migratory success in American shad.

Journal of Fish Biology↗
USGS1999

Metabolic rates in an anadromous clupeid, the American shad ( Alosa sapidissima )

To assess the energetics of migration in an anadromous fish, adult American shad ( Alosa sapidissima ) were swum in a large respirometer at a range of speeds (1.0–2.3 body lengths (BL) s −1 , 13–24 °C). Metabolic rate (M O2 ) was logarithmically related to swimming speed (Bl s −1 ; r 2 = 0.41, slope = 0.23 ± 0.037) and tailbeat frequency (beats × min −1 ; r 2 = 0.52, slope = 0.003 ± 0.0003). Temperature had a significant effect on metabolic rate ( r 2 = 0.41) with a Q 10 of 2.2. Standard metabolic rate (SMR), determined directly after immobilization with the neuroblocker gallamine triethiodide, ranged from 2.2–6.2 mmolO 2 kg −1 h −1 and scaled with mass (W) such that SMR = 4.0 (±0.03)W 0.695(±0.15) . Comparison of directly determined and extrapolated SMR suggests that swimming respirometry provides a good estimate of SMR in this species, given the differences in basal activity monitored by the two methods. Overall, American shad metabolic rates (M O2 and SMR) were intermediate between salmonids and fast-swimming perciforms, including tunas, and may be a result of evolutionary adaptation to their active pelagic, schooling life history. This study demonstrates variability in metabolic strategy among anadromous fishes that may be important to understanding the relative success of different migratory species under varying environmental conditions.

Journal of Comparative Physiology B: Biochemical, ↗
USGS1999

The effect of migration distance and timing on metabolic enzyme activity in an anadromous clupeid, the American shad (Alosa sapidissima)

The American shad (Alosa sapidissima) is a common anadromous fish species with ecological and economic importance on the east coast of North America. This iteroparous species undergoes an energetically costly upriver spawning migration in spring. To evaluate metabolic changes associated with this migration, we assessed the maximum activity of five metabolic enzymes (citrate synthase (CS), phosphofructokinase (PFK), lactate dehydrogenase (LDH), β-hydroxyacyl coenzyme A dehydrogenase (HOAD), alanine aminotransferase (GPT)) in liver, red muscle and white muscle during upstream migration in two successive years in the Connecticut River. For aerobic capacity (CS), glycolytic capacity (LDH) and utilization of stored lipid and protein energy (HOAD and GPT), there is a general pattern of increasing activity with a subsequent decline at the most upriver sites. Red muscle CS activity increased by as much as 40% during the migration while white muscle CS activity was 120% higher in the river than in the ocean. In contrast, muscle anaerobic capacity, indicated by PFK, was low as fish entered the river and then increased 5-fold at the most upriver sites. White muscle HOAD increased ∼30% while red muscle HOAD and muscle GPT increased as much as 60%. There were interannual and sex-associated differences in enzyme activity during upstream migration and through time at a single location. In some cases interannual differences can be larger than those seen during upriver migration as in the case of red muscle CS where sampling years differed by 125%. These interannual differences may be a result of differing river conditions that affect migratory effort. We have demonstrated that American shad use tissue and sex-specific regulation of enzyme activity during migration and we suggest that American shad metabolically acclimate to upstream migration.

Fish Physiology and Biochemistry↗
USGS1999

Regional variation in muscle metabolic enzymes in individual American shad (Alosa sapidissima)

Evaluation of the activity of metabolic enzymes is often used to assess metabolic capacity at the tissue level, but the amount of regional variability within a tissue in an individual fish of a given species is frequently unknown. The activities of four enzymes (citrate synthase (CS), phosphofructokinase, lactate dehydrogenase (LDH), and β-hydroxyacyl coenzyme A dehydrogenase (HOAD)) were assayed in red and white muscle at 10 sites along the body of adult American shad ( Alosa sapidissima ). Red and white muscle HOAD and white muscle CS and LDH varied significantly, generally increasing posteriorly. Maximal variation occurs in red muscle HOAD (~450%) and white muscle LDH (~60%) activity. Differences between the sexes also vary with sampling location. This study suggests that the variability in enzyme activity may be linked to functional differences in the muscle at different locations, and also provides guidelines for sample collection in this species.

Canadian Journal of Zoology↗