Showing papers by "National Marine Fisheries Service published in 1992"

A preliminary evaluation of wave attenuation by four species of seagrass

Abstract: Seagrasses are able to modify current flow and sediment composition, yet little information exists describing their effect on waves. Four species of seagrass, Halodule wrightii, Syringodium filiforme, Thalassia testudinum and Zostera marina were evaluated for their ability to reduce wave energy under various combinations of shoot density and water depths over a 1 m test section in a wave tank. Percent wave energy reduction per meter of seagrass bed equaled 40% when the length of these seagrasses was similar to the water depth. Seagrasses are approximately equal to saltmarshes in reducing wave energy on a unit distance basis, but only when water depth is scaled to plant size. When seagrass beds occur as broad, shallow meadows, the influence of seagrasses on wave energy will be substantial.

Global population structure and natural history of the green turtle (chelonia mydas) in terms of matriarchal phylogeny.

Abstract: To address aspects of the evolution and natural history of green turtles, we assayed mitochondrial (mt) DNA genotypes from 226 specimens representing 15 major rookeries around the world. Phylogenetic analyses of these data revealed (1) a comparatively low level of mtDNA variability and a slow mtDNA evolutionary rate (relative to estimates for many other vertebrates); (2) a fundamental phylogenetic split distinguishing all green turtles in the Atlantic-Mediterranean from those in the Indian-Pacific Oceans; (3) no evidence for matrilineal distinctiveness of a commonly recognized taxonomic form in the East Pacific (the black turtle C.m. agassizi or C. agassizi); (4) in opposition to published hypotheses, a recent origin for the Ascension Island rookery, and its close genetic relationship to a geographically proximate rookery in Brazil; and (5) a geographic population substructure within each ocean basin (typically involving fixed or nearly fixed genotypic differences between nesting populations) that suggests a strong propensity for natal homing by females. Overall, the global matriarchal phylogeny of Chelonia mydas appears to have been shaped by both geography (ocean basin separations) and behavior (natal homing on regional or rookery-specific scales). The shallow evolutionary population structure within ocean basins likely results from demographic turnover (extinction and colonization) of rookeries over time frames that are short by evolutionary standards but long by ecological standards.

Rethinking the Stock Concept: A Phylogeographic Approach

Abstract: The “stock” is the fundamental population unit of legally mandated conservation efforts, yet its formal definition in the scientific literature and in two U.S. conservation acts is varied and so general that attempts to apply it in practice are arbitrary. Because choice of stocks deserving management protection is sometimes politically contentious, improvement of the working definition is important. A key element should be the degree to which a population can be considered an evolutionarily significant unit. We propose that a hierarchial classification scheme be applied to stock designations. Category I populations, having the highest probability of being evolutionarily significant units, are characterized by a discontinuous genetic divergence pattern where locally adapted and closely related genome assemblages are separated from others geographically and by significant genetic distances. Category II populations are similarly characterized by significant genetic diversity, but with weak geographic partitioning. Category III populations are the converse of II, having little genetic differentiation between assemblages that are clearly separate and likely to be reproductively isolated. Category IV assemblages have the lowest probability of being evolutionarily significant units and are characterized by extensive gene flow and no subdivision by extrinsic barriers. In addition to phylogeographic designation, the following information is used in the classification, as indicated by single-letter abbreviations: distribution (a), population response (b), phenotypic (c), and genotypic (d) information. Included are evidence both for and against designating population as a separate stock. In the designation “Type II a/bc,” for example, information to the right of the solidus would be evidence for “lumping,” to the left would be for “splitting.” Missing letter abbreviations would signify lack of reliable data. Note that phylogeographic designation depends on the results of selection operating to produce a locally adapted genome (indicated by differences in demographic, phenotypic, and genotypic measures) and on gene flow (indicated by differences in distribution or by movement data). Hierarchial stock categorization allows resource managers to direct limited resources to the populations most deserving of protection, that is, the populations that are most likely to be evolutionarily significant units. Using this comprehensive classification of stock allows preliminary, conservative splitting of assemblages where data are lacking without the danger that these divisions will become entrenched as biological dogma.

Feedback interactions between zinc and phytoplankton in seawater

Abstract: In Zn ion-buffered media, oceanic species (Thalassiosira oceanica and Emiliania hu.xZeyi) grew at near-maximal rates at the lowest free Zn ion concentration ((Zn2+) = lo- 12,3 M), whereas coastal species (Thalassiosira pseudonana and Thalassiosira weissflogii) were limited at (Zn2+) < lo-" M. The ability of the oceanic species to outgrow coastal ones at low (Zn2+) was due almost entirely to a reduced growth requirement for cellular Zn rather than to an increased capability for uptake. All isolates exhibited similar sigmoidal relationships between cellular Zn: C ratios and (Zn2+) with minimal slopes at (Zn2+) of lO-'o.5 to - 1 O-9.5 M and increasing slopes above and below this range. The minimal slopes at intermediate (Zr?+) could be explained by negative feedback regulation of a high-affinity Zn uptake system, while increased slopes at high (Zn2+) appeared to be related to uptake by a low-affinity site. Measured relationships between cellular Zn : C ratios and (Zn'+) agreed well with those computed from a modified Redfield model based on depth profiles for Zn and PO, concentrations and Zn chelation in the nutricline of the North Pacific. This agreement provides evidence that Zn concentrations in the nutricline are controlled by biological uptake and regen- eration as occurs for major nutrients.

Physiological and behavioural thermoregulation in bigeye tuna ( Thunnus obesus )

Abstract: TUNA are unique among teleost fishes in being thermoconserving. Vascular counter-current heat exchangers maintain body temperatures above ambient water temperature, thereby improving locomotor muscle efficiency, especially at burst speeds and when pursuing prey below the thermocline1–6. Because tuna also occasionally swim rapidly in warm surface waters, it has been hypothesized that tuna thermoregulate to accommodate changing activity levels or ambient temperatures7. But previous field experiments have been unable to demonstrate definitively short-latency, mammalian-type physiological thermoregulation8,9. Here we show using telemetered data that free-ranging bigeye tuna (Thunnus obesus) can rapidly alter whole-body thermal conductivity by two orders of magnitude. The heat exchangers are disengaged to allow rapid warming as the tuna ascend from cold water into warmer surface waters, and are reactivated to conserve heat when they return into the depths. Combining physiological and behavioural thermoregulation expands the foraging space of bigeye tuna into otherwise prohibitively cold, deep water.

Range‐wide survey and estimation of total number of steller sea lions in 1989

Abstract: The first range-wide survey of Steller (northern) sea lions (Eumetopias jubatus) was completed in 1989 with a total of 68,094 adult and juvenile (nonpup) Steller sea lions counted. This total count includes 10,000 in Russia (15% of the range-wide count), 47,960 in Alaska (70%), 6,109 in British Columbia (9%), 2,261 in Oregon (3%), and 1,764 in California (3%). A range-wide pup count was not obtained. We estimated the 1989 world population based on a calculation for total pups and obtained a range-wide estimate of 116,000 total animals, or about 39–48% of the 240,000-300,000 estimated 30 yr ago.

Oxygen transport and cardiovascular responses in skipjack tuna (Katsuwonus pelamis) and yellowfin tuna (Thunnus albacares) exposed to acute hypoxia.

Abstract: Responses to acute hypoxia were measured in skipjack tuna (Katsuwonus pelamis) and yellowfin tuna (Thunnus albacares) (≈1–3 kg body weight). Fish were prevented from making swimming movements by a spinal injection of lidocaine and were placed in front of a seawater delivery pipe to provide ram ventilation of the gills. Fish could set their own ventilation volumes by adjusting mouth gape. Heart rate, dorsal and ventral aortic blood pressures, and cardiac output were continuously monitored during normoxia (inhalant water (PO 2>150 mmHg) and three levels of hypoxia (inhalant water PO 2≈130, 90, and 50 mmHg). Water and blood samples were taken for oxygen measurements in fluids afferent and efferent to the gills. From these data, various measures of the effectiveness of oxygen transfer, and branchial and systemic vascular resistance were calculated. Despite high ventilation volumes (4–71·min-1·kg-1), tunas extract approximately 50% of the oxygen from the inhalant water, in part because high cardiac outputs (115–132 ml·min-1·kg-1) result in ventilation/perfusion conductance ratios (0.75–1.1) close to the theoretically ideal value of 1.0. Therefore, tunas have oxygen transfer factors (ml O2·min-1·mmHg-1·kg-1) that are 10–50 times greater than those of other fishes. The efficiency of oxygen transfer from water in tunas (≈65%) matches that measured in teleosts with ventilation volumes and order of magnitude lower. The high oxygen transfer factors of tunas are made possible, in part, by a large gill surface area; however, this appears to carry a considerable osmoregulatory cost as the metabolic rate of gills may account for up 70% of the total metabolism in spinally blocked (i.e., non-swimming) fish. During hypoxia, skipjack and yellowfin tunas show a decrease in heart rate and increase in ventilation volume, as do other teleosts. However, in tunas hypoxic bradycardia is not accompanied by equivalent increases, in stroke volume, and cardiac output falls as HR decreases. In both tuna species, oxygen consumption eventually must be maintained by drawing on substantial venous oxygen reserves. This occurs at a higher inhalant water PO2 (between 130 and 90 mmHg) in skipjack tuna than in yellowfin tuna (between 90 and 50 mmHg). The need to draw on venous oxygen reserves would make it difficult to meet the oxygen demand of increasing swimming speed, which is a common response to hypoxia in both species. Because yellowfin tuna can maintain oxygen consumption at a seawater oxygen tension of 90 mmHg without drawing on venous oxygen reserves, they could probably survive for extended periods at this level of hypoxia.

A two-receptor model for salmon gonadotropins (GTH I and GTH II).

Abstract: The possible existence of distinct receptors for salmon gonadotropins (GTH I and GTh II) and the distribution of the receptor(s) were studied through examination of the binding of coho salmon (Oncorbynchus kistuch) GTh I and GTH II to membranes from thecal layers and granulosa cells of salmon ovaries. Purified coho salmon gonadotropins were iodinated by the lactoperoxidase method. Crude membrane preparations were obtained from thecal layers, granulosa cells, and whole ovaries of coho salmon in the postvitdllogenic/preovulatory phase. Binding of “5I-GTH I to membranes from thecal layers, granulosa cells, and whole ovaries, and binding of “51-GTh II to thecal layer cell membranes could be inhibited by both GTHs, but GTh I was more potent than GTh II. In contrast, GTh II was more potent than GTh I in inhibiting “5I.GTH II binding to membranes from granulosa cells and whole ovaries, but the inhibition curves were not parallel. Scatchard plot analysis suggested that there was a single type of receptor in the thecal layers for both GTHs, whereas in the granulosa cells there was more than one type of receptor for both GTHs. Based on these results, a two-receptor model for the postvitdllogenic/preovulatory salmon ovary is proposed with the following features: 1) there are two types of gonadotropin receptors in the salmon ovary, type I and type IL; 2) the type I receptor binds both GTHs, but with higher affinity for GTh I, whereas the type II receptor is highly specific for GTh II and may have only limited interaction with GTh I; and 3) the type I receptor is present in both thecal cells and granulosa cells, whereas the type II receptor is present in granulosa cells.

Validated age and growth of the leopard shark, Triakis semifasciata, with comments on reproduction

Abstract: The age, growth, and sexual maturation of the leopard shark, Triakis semifasciata, from central California were studied. Growth band counts in vertebral centra of 162 leopard sharks produced von Bertalanffy growth curves with L∞, K. and to parameters of 1536 mm. 0.082, and -2.31, respectively, for both sexes combined. The L8 value for females (1602 mm TL) was slightly but insignificantly higher than for males (1499 mm TL), but the K and to values were almost identical. Seasonal changes in size modes of young-of-the-year leopard sharks, centrum edge characteristics, and growth and tetracycline mark-recapture from the field were used to validate annual deposition of vertebral centrum band pairs. Sexual maturity was evaluated by the gonads and presence of sperm and eggs; males mature at 7 yr and at about 63% of asymptotic length, and females mature at 10 yr, and at about 72% of asymptotic length. This slow growth, late maturity, and relatively low fecundity may increase their susceptibility to over-exploitation.

DNA as a solar dosimeter in the ocean.

Abstract: Stratospheric ozone depletion may result in increased solar UV-B radiation to the ocean's upper layers and may cause deleterious effects on marine organisms. The primary UV-B damage induced in biological systems is to DNA. While physical measurements of solar UV-B penetration into the sea have been made, the effective depth and magnitude of actual DNA damage have not been determined. In the experiments reported here, UV-B-induced photoproducts (cyclobutane pyrimidine dimers) have been quantified in DNA molecules exposed to solar UV at the surface and at various depths in clear, tropical marine waters off Lee Stocking Island (23 degrees 45' N, 76 degrees 0.7' W), Exuma Cays, Bahamas. (14C)thymidine-labeled DNA or unlabeled bacteriophage phi X174 DNA was placed in specially designed quartz tubes at various depths for up to five days. Following exposure, DNA samples were removed to the laboratory where UV-B-induced pyrimidine dimers were quantified using a radiochromatographic assay, and bacteriophage DNA inactivation by solar UV-B was assayed by plaque formation in spheroplasts of Escherichia coli. Pyrimidine dimer induction was linear with time but the accumulation of dimers in DNA with time varied greatly with depth. Attenuation of dimer formation with depth of water was exponential. DNA at 3 m depth had only 17% of the pyrimidine dimers found at the surface. Bacteriophage phi X174 DNA, while reduced 96% in plaque-forming ability by a one day exposure to solar UV at the surface of the water, showed no effect on plaque formation after a similar exposure at 3 m. The data collected at the water's surface showed a "surface-enhanced dose" in that DNA damages at the real surface were greater than at the imaginary surface, which was obtained by extrapolating the data at depth to the surface. These results show the sensitivity of both the biochemical (dimers) and biological (phage plaques) DNA dosimeters. DNA dosimeters offer a sensitive, convenient and relatively inexpensive monitoring system, having both biochemical and biological endpoints for monitoring the biologically effective UV-B flux in the marine environment. Unlike physical dosimeters, DNA dosimeters do not have to be adjusted for biological effectiveness since they are sensitive only to DNA-mediated biologically effective UV-B radiation. Results of pyrimidine dimer induction in DNA by solar UV accurately predicted UV doses to the phage DNA.

Diving and haulout behavior of crabeater seals in the Weddell Sea, Antarctica, during March 1986

Abstract: Time-depth recorders were used to study the diving and haulout behavior of six crabeater seals in the marginal. ice edge zone of the Weddell Sea during March 1986. Haulout patterns revealed the seals' clear preference for diving during darkness and hauling out onto sea ice during daylight. Seals did not necessarily haul out every day; individual seals hauled out on 80–100% of days during the study period. Four general dive types were identified: 1) traveling dives, 2) foraging dives, 3) crepuscular foraging dives, and 4) exploratory dives. Nearly continual diving occurred for extended periods (about 16 h) nightly, with one individual diving up to 44 h without interruption. Foraging dives occurring during crepuscular periods were deeper than those made during the darkest hours. The authors suggest that the distinct diel pattern of dive timing and depth may be related to possible predator avoidance behavior by the seals' principal prey, Antarctic Krill.

Notes: Comparison of Predator Avoidance Capabilities with Corticosteroid Levels Induced by Stress in Juvenile Coho Salmon

Abstract: The relationship between predator avoidance deficits induced by a simple handling stress and the level of plasma corticosteroids was determined for juvenile coho salmon Oncorhynchus kisutch. Groups of fish were held out of water for 1 min, then allowed to recover from this stress for 1, 90, or 240 min. After each recovery period, some unstressed and stressed fish were sampled for plasma cortisol, and others were subjected to predation by lingcod Ophiodon elongatus. Levels of corticosteroids in stressed fish remained high throughout the 240-min period of recovery, but predator avoidance returned to control levels in less than 90 min. Results suggest that juvenile coho salmon quickly recover basic survival skills of predator avoidance after mild stress, even though cortisol levels continue to indicate a stressed condition.

Pollution and developmental abnormalities of Atlantic fishes

Abstract: Planktonic ‘eggs’ of Atlantic mackerel,Scomber scombrus, provide evidence that pollution is associated with mortality, malformation, and abnormal chromosome division of fish embryos developing about the surface of the U.S. Atlantic coast. Embryo data are substantiated by the finding that adults of mackerel, windowpane flounder,Scophthalmus acquosus, and winter flounder,Pseudopleuronectes americanus, from more polluted coastal areas also have higher frequencies of mitotic abnormality than those from less polluted regions of the Mid- and North Atlantic. No ontogenetic interval escapes contamination. All are likely to be adversely influenced, resulting in considerable direct and indirect cumulative effect on total early-life survival. Development of genetic and epigenetic resistance to reproductively harmful influences of contaminants may interfere with other modifications in structure and function necessitated by natural environmental fluctuations, changes in climate, and by fishing itself.

Winter Flounder Movements in the Inner New York Bight

Abstract: Winter flounder Pleuronectes americanus collected in the inner New York Bight were tagged and released to determine generalized movement patterns. Between July 1986 and August 1989, there were 7,346 winter flounder (≥18 cm) tagged at 14 inshore stations in Sandy Hook, Raritan, and Lower bays and the Shrewsbury River and at 22 offshore stations associated with a sewage sludge dumpsite 22 km off the New Jersey coast. Results from 206 tag returns indicated that the Navesink–Shrewsbury river system, part of the Sandy Hook–Raritan estuary, supports a population of winter flounder that returns yearly during the spawning season. Winter flounder exhibited limited seasonal migration and intermixed with other winter flounder from the inner New York Bight, indicating the existence of a dynamic assemblage.

Riverine Spawning by Sockeye Salmon in the Taku River, Alaska and British Columbia

Abstract: Radio telemetry was used to determine the distribution of sockeye salmon Oncorhynchus nerka returning to spawn in the glacial Taku River in 1984 and 1986, and to locate and characterize spawning areas used by this species. During the study, 253 sockeye salmon were tracked as they moved upriver; 204 of these were followed to spawning areas. Only 37% of the 204 fish traveled to areas associated with lakes; the remaining 63% returned to “riverine” areas – river areas without lakes (42% to the Taku River main stem, 17% to the Nakina River, and 4% to other rivers). Sockeye salmon spawning in riverine areas used a variety of habitat types, including main-river channels, side channels, tributary streams, and upland sloughs. Most (55%) of the radio-tagged fish that returned to the Taku River main stem were tracked to side-channel spawning areas. Half of the 471 adult sockeye salmon sampled in main-stem spawning areas had migrated to sea as juveniles before their first winter. This study showed that many ...

The influence of ocean currents on latitude of landfall and migration speed of sockeye salmon returning to the Fraser River

Abstract: We hypothesize that the interannual variability of the Northeast Pacific Ocean circulation affects the latitude of landfall and migration speed of adult sockeye salmon (Oncorhynchus nerka) returning to the Fraser River. The Ocean Surface Current Simulations (OSCURS) model was used to simulate the return migration paths of compass-orientated sockeye for two years: 1982, which had a weak Alaska Gyre circulation and low Northern Diversion Rate (defined as the percentage of sockeye returning around the north end of Vancouver Island instead of the south end); and 1983, with a strong circulation and high northern diversion rate. The majority of model sockeye made landfall further north in 1983 than in 1982. The difference in landfall between 1983 and 1982 depended on the migration start position, swim speed, direction of orientation, and migration start date. The currents assisted the shoreward migration of sockeye starting from south of 55o N and impeded the migration of sockeye starting from further north. The simulation results were consistent with our hypothesis and suggest that the effects of the Northeast Pacific currents must be included in sockeye migration models. We propose a conceptual model for the prediction of the Northern Diversion Rate that includes Blackbourn's (1987) temperature-displacement model, enhanced to include the effects of currents during the ocean phase of migration, and the use of two predictive formulas for the coastal phase of migration: the formula of Xie and Hsieh (1989) for sockeye approaching Vancouver Island directly from the ocean, and a yet-to-be-developed formula for sockeye approaching from within the Coastal Downwelling Domain directly to the north of Vancouver Island.

Age, growth, and size distribution of larval Atlantic menhaden off North Carolina

Abstract: Counts of growth increments on sagittal otoliths of larval Atlantic menhaden Brevoortia tyrannus spawned and reared in the laboratory showed that 1 increment/d was formed beginning 5 d after fertilization and that increment counts could be used to estimate larval age, A Gompertz growth equation described the relationship between age and standard length (SL) for 353 larvae collected off North Carolina in fall and winter, 1979–1980. Larvae grew from 3.4 mm SL at hatching to 25.2 mm SL at 100 d. Age of larvae varied inversely with capture distance from shore, Age distribution of larvae on the North Carolina continental shelf suggests that transport of larvae from offshore spawning sites to the estuary was biphasic. Transport was relatively rapid to within about 35 km of shore and relatively slow from there to shore, Mean age at estuarine recruitment increased from 40 to 80 d throughout the recruitment season, which may represent differences in transport rate.

Okadaic acid inhibits a protein phosphatase activity involved in formation of the mitotic spindle of GH4 rat pituitary cells.

Abstract: Okadaic acid, a selective inhibitor of serine/threonine protein phosphatases, was utilized to investigate the requirement for phosphatases in cell cycle progression of GH4 rat pituitary cells Okadaic acid inhibited GH4 cell proliferation in a concentration-dependent manner with a half-maximal inhibition (IC50) of approximately 5 nM Treatment of GH4 cells with 10 nM okadaic acid resulted in a 40-60% decrease in phosphatase activity and an increase in the proportion of phosphorylated retinoblastoma (RB) protein Cell cycle analysis indicated that okadaic acid increased the percentage of cells in G2-M, decreased proportionally the percentage of cells in G1 phase, and had little effect on the percentage of cells in S-phase The absence of a change in the proportion of S-phase cells indicates that G1-specific phosphatases responsible for dephosphorylation of RB protein were not inhibited by 10 mM okadaic acid Mitotic index revealed that 10 nM okadaic acid decreased proliferation of GH4 cells specifically by slowing the progression through mitosis Immunostaining with anti-tubulin demonstrated that 10 nM okadaic acid-treated mitotic cells contained mitotic spindles; however, the spindle apparatus in these cells frequently contained multiple poles These results suggest that the organization of spindle microtubules during prometaphase requires a protein phosphatase that is sensitive to nanomolar concentrations of okadaic acid Chromosomes in 10 nM okadaic acid-treated cells appear to be attached to spindle microtubules and the nuclear envelope is absent The effects of okadaic acid on the spindle differ from those elicited by the calcium channel blocker, nimodipine, indicating that this okadaic acid sensitive phosphatase is not part of the calcium signalling events which participate in mitotic progression

Aggregations of myctophid fishes with other pelagic fauna

Abstract: Direct underwater observations of myctophid fishes were conducted to 630 m in submarine canyons along the outer margin of the northeast United States continental shelf with the Johnson-Sea-Link II submersible. Data revealed that myctophids occurred in aggregations of other pelagic fauna (e.g., ctenophores, sergestids, amphipods) when densities of the former were low but the latter were high. We suggest that myctophids selectively occur with other pelagic fauna to reduce the probability of direct contact with predators and to take advantage of aggregate search abilities for common prey taxa.