Habitat use by spawning adult, egg, and larval American shad in the Delaware River
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Rivers↗
Geology topics
T. W. H. Backman
Publications and source records attributed to T. W. H. Backman.
Evaluation of habitat suitability index models for riverine life stages of American shad, with proposed models for premigratory juveniles
No abstract available at this time
Biological Report↗
Notes: Group-size-mediated metabolic rate reduction in American shad
The relation of oxygen consumption to ambient temperature and group size was studied in juvenile American shad Alosa sapidissima at three group sizes: 5 or 6 (small), 9–13 (medium), and 41–48 (large) fish per 500‐L tank. Oxygen consumption rates, water temperatures, and behavior were measured concurrently in the three group‐size treatments. Schooling predominated in large groups, whereas aggregating behavior dominated medium and small groups. Fish in small or medium groups consumed oxygen at two to four times the rate of fish in large groups (0.36 or 0.25 versus 0.11 mg O 2 /[g biomass·h]). This group‐size‐related respiratory rate reduction could be caused by the effect of calming, type of swimming, swimming speed, or hydrodynamic advantage.
Transactions of the American Fisheries Society↗
Larval American shad: Effects of age and group size on swimming and feeding behavior
We analyzed the behavior of 3–4‐d‐old prolarval and 28–33‐d‐old metalarval American shad Alosa sapidissima in groups of 3–1,000 fish per 22‐L glass tank, to determine whether (1) previously described juvenile behavior patterns first develop in larvae, (2) group size or density alters the behavior of larvae, and (3) schooling or other forms of cohesive behavior develop in larvae to promote social interactions. Twelve discrete behaviors or modal action patterns (MAPS) oflarvae were observed at all group sizes; halfthese patterns are unique to larval stages. Conversely, larvae do not develop five previously described juvenile MAPS. Stereotyped metalarval feeding sequences were absent or poorly developed in prolarvae. Group size was directly related to duration of free swimming in water column (metalarvae only) and to frequencies of “proximity to another fish” (all larvae), “contact another fish” (all larvae), and “escape or flee” (all larvae). Age or larval stage significantly affected all swimming‐related activities and three feeding behaviors. Larvae foraged and fed independently of one another and used MAPs typical of other larval fishes (“fixate,” “sigmoid,” “lunge,” and “capture”). With one exception (a direct relationship between frequency of food capture and metalarval size), group size and individual size did not significantly affect larval feeding success. Neither schooling nor forms of behavior leading to coordinated group swimming were observed at either larval stage. Larval behavior differed from juvenile behavior in a way that suggests survival in riverine habitats is promoted by behavior that disperses larvae and enables them to function nonsocially.
Transactions of the American Fisheries Society↗
Genotypic and phenotypic variability of Zostera marina on the west coast of North America
The relation between environmental factors and leaf morphology of Zostera marina L. have long been unclear, primarily because the species is intrinsically variable. The common-garden method was used to determine the genetic, environmental, and interaction components of leaf size variation. Zostera marina consists of several ecotypes with a wide range of phenotypic plasticity. Variation in the morphology of Z . marina was of three types: genetic, accounting for 14% across the localities studied; environmental (phenotypic plasticity along temporal and spatial gradients), accounting for 32%; and interaction between genotype and environmental, acounting for 35%. Five ecotypes were described for the North American Pacific coast: Z . marina L. var. izembekensis Backman, Z . marina L. var. typica Setchell, Z . marina L. var. phillipsii Backman, Z . marina L. var. latifolia Morong, Z . marina L. var. atàm Backman. Temporal variation was due to seasonal phenotypic changes in ecotypes. Zostera marina var. izembekensis showed little seasonal morphological changes; Z . marina var. typica demonstrated minor increase in leaf size in spring and summer. Zostera marina var. phillipsii and Z . marina var. latifolia behaved similarly in that leaf size of both increased markedly in spring through early summer. Zostera marina var. phillipsii is adapted to Hood Canal and Puget Sound while Z . marina var. latifolia occupies the outer coast. Zostera marina var. atàm exhibits sexual reproduction exclusively and is specifically adapted to the Gulf of California.
Canadian Journal of Botany↗
Tolerance of subyearling American shad to short-term exposure to gas supersaturation
Subyearling American shad Alosa sapidissima normally migrate from rivers in the fall and may encounter changes in gas supersaturation levels while traversing hydroelectric dams. To determine whether changes in behavior or survival occur during these events, we exposed subyearling American shad to five levels of gas supersaturation that included pressure increases above equilibrium (▵P) from 10 to 205 mm Hg (101–128% saturation) for 4 h. Multifactor analysis of variance showed no significant differences in behavior or survival of fish before or after treatment. Gas bubbles were observed on external tissues of fish only at the highest treatment level (▵P = 205 mm Hg). Factor analysis elucidated three categories of behavioral organization under experimental conditions: boundary, social, and nonsocial behavior. Under gas supersaturation conditions thought to occur in dammed rivers of the eastern USA, the behavior of subyearling American shad does not appear to be affected in a way that might reduce survival during migration.
North American Journal of Fisheries Management↗
Subyearling American shad concentrate in swifter current in the upper Delaware River
No abstract available.
Delaware River↗
Comparison of three techniques for the capture and transport of impounded subyearling American shad
A comparison of three techniques for the capture of impounded juvenile American shad ( Alosa sapidissima ; 50–100 mm total length) showed a 1‐m‐diameter entrainment net to be an order of magnitude more efficient than a black rectangular tank, which relied on a light source to attract the fish at night. A third technique, pond drawdown, was by far the most efficient, but it also resulted in high (>50%) short‐term mortality. American shad captured by the first two techniques were transported a short distance and placed in circular holding tanks (1.22 or 2.44 m in diameter). After initial treatment with 0.5% sea salts for 1 d and continued culture in 13–15°C water, these fish schooled and fed normally within 1 week, and there was no mortality within 48 h after transfer. Weekly overall mortality rates ranged from 1.8 to 8.4%. Regression analysis showed a significant inverse relation between weekly mortality and number of fish per tank, suggesting that relatively large numbers offish in transport or holding tanks may reduce mortality by promoting stress‐mitigating schooling behavior.
Progressive Fish-Culturist↗