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R. M. Ross

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

At least 37 records · Page 2Linked to original sources
USGS1998

Immunocytochemical and ultrastructural identification of pituitary cell types in the protogynous Thalassoma duperrey during adult sexual ontogeny

Protogynous wrasses (Thalassoma duperrey): females (F), primary males (PM) along with a few terminal-phase males (TM) and sex-changed males (SM), were used to characterize the topographical organization of the pituitary. In general, immunocytochemical and ultrastructural features of the adenohypophyseal cell types of the saddleback wrasse pituitary resemble those of other teleosts. In the rostral pars distalis (RPD), corticotropic cells were found bordering the neurohypophysis (NH) and surrounding the centroventrally located prolactin cells. Thyrotropic cells formed a small group in the anteriodorsal part of the rostral and proximal pars distalis (PPD). The somatotropic cells were distributed in large clusters, mostly organized in cell cords around the interdigitations of the NH of the dorsal PPD. Cells containing gonadotropin I?? subunit were localized in the dorsal parts of the PPD, in close association with somatotropic cells and gonadotropin II?? subunit containing cells were seen in the centroventral parts of the PPD and along the periphery of the pars intermedia (PI). The pars intermedia was composed of melanotropic cells and somatolactin cells that lined the neurohypohysis. Distinct ultrastructural differences in corticotropic and somatotropic cells were not observed between the four groups. In all groups, prolactin cells in the ventral-most RPD could be immature cells or actively secreting prolactin. Gonadotropic II cells of PM and F had relatively higher incidence of "nuclear budding" and cell organelles compared to TM and SM. Besides gonadotropic, the active melanotropic and somatolactin cells might be associated with some aspect(s) of reproduction.

Zoological Science↗
USGS1997

Evidence of secondary consumption of invertebrate prey by Double-crested Cormorants

The piscivorous nature of the Double-crested Cormorant (Phalacrocorax auritus) is well documented. However, many researchers who have used regurgitated pellets to describe the diet of cormorants report that invertebrates compose a small but consistent portion of the diet. We examined the hypothesis that invertebrates found in pellets are primarily the result of secondary consumption. We used odds ratio analysis to examine associations in 2,846 individual pellets between the presence of specific invertebrate prey and the presence of fish species known to consume those invertebrate taxa. Significant (P < 0.05) relationships occurred between gastropods and pumpkinseed (Lepomis gibbosus) and ictalurids, and between decapods and rock bass (Ambloplites rupestris) and smallmouth bass (Micropterus dolomieu). Significant (P < 0.05) relationships were also found between pelecypods and pumpkinseed and ictalurids. We suggest that the invertebrate prey we observed in pellets were present in the digestive tracts of fish that were consumed by Double-crested Cormorants and hence represent secondary consumption by cormorants. We conclude that consumption of invertebrates by Double-crested Cormorants may be overestimated in the literature in instances where the diet was described using pellets.

Waterbirds↗
USGS1996

Pellets versus feces: their relative importance describing the food habits of double-crested cormorants

We compared the amount of taxonomically identifiable (diagnostic) fish remains in double-crested cormorant ( Phalacrocorax auritus ) feces to that exiting the birds via regurgitated pellets. Feces and pellets were collected concurrently during June 1994 from cormorant colonies on Little Galloo Island, eastern Lake Ontario. About 90% of the diagnostic fish remains were found in pellets and 10% in feces. However, only 4% of the diagnostic remains in the feces represented fish that could not be accounted for in the pellets. Pellets provided better information than feces for determining diet composition. Because of the increased effort to collect and analyze fecal material, and the limited amount of additional information provided, examination of feces in addition to pellets is probably not necessary in most studies of double-crested cormorant feeding ecology.

Journal of Great Lakes Research↗
USGS1995

Growth and mortaility rates of larval American shad, Alosa sapidissima, at different salinities

The tolerance of post yolk-sac American shad Alosa sapidissima larvae to salinities typically seen in estuaries was assessed experimentally. Sixteen-day-old Hudson River (experiment I) and 35-d-old Delaware River (experiment II) larvae were held for 8 d and 9 d respectively in low (0–1‰), medium (9–11‰), and highly (19–20‰) brackish water, and mortality and growth rates were measured. Growth rates did not vary significantly among salinity treatments. Mortality in experiment I did not vary significantly among salinity treatments however, in experiment II, mortality was zero at 10‰ but higher and statistically indistinguishable between 0‰ and 20‰ In experiment II relative condition increased with salinity. These results imply that estuarine salinities neither depress growth rates nor elevate mortality rates of larval American shad when compared with freshwater conditions. We conclude that ecological factors other than the physiological effects of salinity have played more important roles in the evolution of the upriver spawning and nursery preference shown by this species.

Delaware, New Jersey, New York, Philadelphia↗
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↗
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↗