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R. M. Ross

Publications and source records attributed to R. M. Ross.

53 records · Page 3Linked to original sources
USGS1993

Morphometric differentiation of American shad and white sucker eggs from riverine samples

We developed a statistical method to distinguish the large demersal eggs of American shad from those of white sucker in riverine samples using egg morphometric analysis. Eggs were first screened by total diameter in deionized water according to ranges reported in the published literature. Differences in relative yolk diameter between the two species were then determined statistically from known museum sources. Only those eggs with relative yolk diameters greater than two standard deviations below the mean for white sucker eggs were considered to be American shad eggs. The criteria for American shad eggs were total diameter ≥2.3 nm and relative yolk diameter ≤66%. A partial test of the model showed predicted identity to agree with observed identity for 74 out of 75 shad eggs.

Journal of Freshwater Ecology↗
USGS1993

Evaluation of the anesthetic metomidate for the handling and transport of juvenile American shad

Juvenile American shad ( Alosa sapidissima ) were exposed to three levels of metomidate (0.0 = control, 0.5, and 1.0 mg/L) and three types of sedation or handling (none, sedation only, and handling after sedation) to determine the efficacy and safety of the drug for use in transport and handling of this species. Mean sedation times were 9 and 3 min, and mean recovery times were 6 and 7 min, respectively, for the 0.5‐ and 1.0‐mg/L concentrations of metomidate. For fish exposed to 1.0 mg metomidate/L, normal swimming behavior was delayed as long as 4 h after fish were placed in drug‐free water. Aggregating and parallel orientation behaviors, precursors of normal schooling, were significantly reduced at the highest drug level for 1 h, but not for 24 h, after recovery. No posttreatment difference in behavior was observed as a result of handling fish (removal from water, weighing, and measuring) under sedation. Long‐term (50‐d) survival was not affected by drug concentration in one experiment and was improved by use of the anesthetic in a second study. Metomidate appears to be useful and safe for the transportation and handling of juvenile American shad.

Progressive Fish-Culturist↗
USGS1992

Mechanisms and function of school formation in subyearling American shad (Alosa sapidissima)

Summary The behavioural repertoire of subyearling American shad ( Alosa sapidissima ) was studied in the laboratory to examine pathways leading to Aggregation and School formation at various group sizes (3–100 fish per 500-liter tank). Three hypotheses were tested: (1) schooling is the dominant behavioural activity of subyearling American shad, (2) development and maintenance of cohesive social behaviour is affected b group size, and (3) survival is a function of group size. Seventeen discrete behaviour patterns were observed. In relation to group size, the amount of time spent Schooling varied directly whereas Following and Aggregating varied inversely. The number of bouts of Parallel orient, Parallel swim, and Pivot also varied inversely with group size. A conceptual model was developed and tested to show how normal schooling behaviour is achieved in small or fragmented groups through intermediary modal action patterns. Sequence analysis showed behavioural diversity to diminish with group size, thereby increasing group cohesion and uniformity of response to stimuli. Probability of survival, determined from weekly mortality in experimental tanks, increased significantly with group size (0.87–0.98 for 3–100 fish). It is hypothesized that survival improves with an increase in the proportion of time spent Schooling, which may increase feeding efficiency, reduce stress, or reduce metabolic expenditures.

Journal of Applied Ichthyology↗
USGS1992

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↗
USGS1992

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↗
USGS1991

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↗
USGS1990

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↗
USGS1989

Biogeography of marine podocopid Ostracodes in Micronesia

Shallow-water podocopic marine Ostracoda from Micronesian lagoons in the Marianas, Caroline, Marshall and Gilbert Islands in the western Pacific were analysed to establish their diversity and zoogeography within Micronesia and the taxonomic affinities with ostracodes from other tropical regions. Sixty-four bottom lagoonal sediment samples from twelve islands and atolls yielded more than seventy species representing over thirty-two ostracode genera. Q-mode cluster analysis using Jaccard coefficients showed that, with few exceptions, all or most samples from a particular lagoon form distinct subgroups (Jaccard=0.45-0.50). At lower levels, five groups delineate faunal regions within Micronesia: the Gilbert Islands (Onotoa) in the southeast part of the region, the northern Marshall Islands (Enewetak, Rongelap, Bikini), the southestern Marshall Islands (Kwajalein, Jaluit, Majuro, Arno), the Marianas and Caroline Islands (Guam, Truk, Pohnpei) and Pingelap. Patterns of species diversity show Guam, Truk, Pohnpei, Pingelap, Kwajalein and Onotoa have the highest species richness (S=32-42) and Shannon-Wiener diversity values (H(S)=2.62-3.02) in the study area. Enewetak, Jaluit, Majuro and Arno show lower values (S=23-27, H(S)=2.29-2.70). Of the ostracode species living in Micronesia, 64.3% have Indo-West Pacific affinities, 7.1% are circumtropical, 5.7% have East Pacific-Caribbean affinities, 11.4% are endemic to Micronesia, and 11.4% have unknown affinities. If the southeast Asian region is a primary species-source, the results show that each Micronesian lagoon is equally likely to be colonized by dispersal from the source region, despite differences in distance from a hypothetical source. However, each lagoon has a distinct ostracode assemblage, probably the result of unique history of random colonization events, local extinctions and environmental disturbances.

Journal of Biogeography↗