Showing papers by "National Marine Fisheries Service published in 2001"

Migratory movements, depth preferences, and thermal biology of Atlantic bluefin tuna.

Abstract: The deployment of electronic data storage tags that are surgically implanted or satellite-linked provides marine researchers with new ways to examine the movements, environmental preferences, and physiology of pelagic vertebrates. We report the results obtained from tagging of Atlantic bluefin tuna with implantable archival and pop-up satellite archival tags. The electronic tagging data provide insights into the seasonal movements and environmental preferences of this species. Bluefin tuna dive to depths of >1000 meters and maintain a warm body temperature. Western-tagged bluefin tuna make trans-Atlantic migrations and they frequent spawning grounds in the Gulf of Mexico and eastern Mediterranean. These data are critical for the future management and conservation of bluefin tuna in the Atlantic.

Population structure of Atlantic salmon (Salmo salar L.): a range-wide perspective from microsatellite DNA variation

Abstract: Atlantic salmon (n = 1682) from 27 anadromous river populations and two nonanadromous strains ranging from south-central Maine, USA to northern Spain were genotyped at 12 microsatellite DNA loci. This suite of moderate to highly polymorphic loci revealed 266 alleles (5-37/locus) range-wide. Statistically significant allelic and genotypic heterogeneity was observed across loci between all but one pairwise comparison. Significant isolation by distance was found within and between North American and European populations, indicating reduced gene flow at all geographical scales examined. North American Atlantic salmon populations had fewer alleles, fewer unique alleles (though at a higher frequency) and a shallower phylogenetic structure than European Atlantic salmon populations. We believe these characteristics result from the differing glacial histories of the two continents, as the North American range of Atlantic salmon was glaciated more recently and more uniformly than the European range. Genotypic assignment tests based on maximum-likelihood provided 100% correct classification to continent of origin and averaged nearly 83% correct classification to province of origin across continents. This multilocus method, which may be enhanced with additional polymorphic loci, provides fishery managers the highest degree of correct assignment to management unit of any technique currently available.

Movements and Population Structure of Humpback Whales in the North Pacific

Abstract: Despite the extensive use of photographic identification methods to investigate humpback whales in the North Pacific, few quantitative analyses have been conducted. We report on a comprehensive analysis of interchange in the North Pacific among three wintering regions (Mexico, Hawaii, and Japan) each with two to three subareas, and feeding areas that extended from southern California to the Aleutian Islands. Of the 6,413 identification photographs of humpback whales obtained by 16 independent research groups between 1990 and 1993 and examined for this study, 3,650 photographs were determined to be of suitable quality. A total of 1,241 matches was found by two independent matching teams, identifying 2,712 unique whales in the sample (seen one to five times). Site fidelity was greatest at feeding areas where there was a high rate of resightings in the same area in different years and a low rate of interchange among different areas. Migrations between winter regions and feeding areas did not follow a simple pattern, although highest match rates were found for whales that moved between Hawaii and southeastern Alaska, and between mainland and Baja Mexico and California. Interchange among subareas of the three primary wintering regions was extensive for Hawaii, variable (depending on subareas) for Mexico, and low for Japan and reflected the relative distances among subareas. Interchange among these primary wintering regions was rare. This study provides the first quantitative assessment of the migratory structure of humpback whales in the entire North Pacific basin.

The evolutionary enigma of bonefishes (albula spp.): cryptic species and ancient separations in a globally distributed shorefish

Abstract: Many examples of cryptic marine species have been demonstrated with biochemical and molecular studies. In most cases, a broadly distributed taxon is actually a group of sibling species that can be distinguished (upon closer examination) by ecological or morphological characters. Fishes of the family Albulidae constitute a notable exception. Bonefish (Albula spp.) morphology and ecology are highly conserved around the globe, and their extended pelagic larval stage could allow population connections on a vast geographic scale. Based on this perceived homogeneity, bonefishes were classified as a single pantropical species, A. vulpes. However, allozyme studies of Hawaiian populations indicated that two sympatric species (A. glossodonta and A. neoguinaica) are included in the synonymy of A. vulpes. To ascertain the number and distribution of evolutionary partitions in Albula, we surveyed 564 bp of mitochondrial DNA (mtDNA) cytochrome b from 174 individuals collected at 26 locations. Sequence compariso...

The road to extinction is paved with good intentions: negative association of fish hatcheries with threatened salmon.

Abstract: Hatchery programmes for supplementing depleted populations of fish are undergoing a worldwide expansion and have provoked concern about their ramifications for populations of wild fish. In particular, Pacific salmon are artificially propagated in enormous numbers in order to compensate for numerous human insults to their populations, yet the ecological impacts of this massive hatchery effort are poorly understood. Here we test the hypothesis that massive numbers of hatchery-raised chinook salmon reduce the marine survival of wild Snake River spring chinook, a threatened species in the USA. Based on a unique 25-year time-series, we demonstrated a strong, negative relationship between the survival of chinook salmon and the number of hatchery fish released, particularly during years of poor ocean conditions. Our results suggest that hatchery programmes that produce increasingly higher numbers of fish may hinder the recovery of depleted wild populations.

Impacts of demographic variation in spawning characteristics on reference points for fishery management

Abstract: Parametric relationships of recruitment to an index of parental stock size assume the latter is proportionally related to spawning potential, irrespective of the demographic composition of adults. Recent empirical information, however, suggests that reproduction by older and experienced females is more successful than by young and inexperienced females. New models are developed incorporating the proportion of each age group spawning for the first, second, etc., time (from information contained in the maturity ogive) and differences in the survival of eggs and larvae in relation to the demography of spawners (based on experimental results). A series of spawning metrics [spawning-stock biomass (SSB), egg production, hatched egg production, viable larval production] and associated recruitment-based fishing mortality reference points (Fmed ,F crash, and the F that allows at least one lifetime spawning per recruit) are contrasted for the Georges Bank Atlantic cod (Gadus morhua) stock. The time-series of spawning intensity is significantly altered when hatched eggs or viable larvae are used as the metric, reflecting the contribution of first- and second-time spawners in some years, and the increasing trend in F. The effect of reduced average maternal size in relation to egg viability was a more important factor contributing to discrepancies with SSB than was spawning experience in relation to hatching success. Percent maximum spawning potential (%MSP) per recruit curves in relation to F are steeper (i.e. result in lower values of %MSP for a given F) for hatched eggs and viable larvae than for SSB or egg production per recruit. Lifetime expected numbers of spawnings per recruit are significantly reduced when the effects of spawning experience on egg hatching success are included. And finally, although point estimates of Fmed and Fcrash are similar using SSB and viable larval production, the median Fcrash estimated from 5000 bootstrap realizations of the Beverton-Holt stock recruitment curve for viable larvae is much lower than that from SSB, with narrower confidence bounds. Our results suggest that traditional approaches to F-based reference points using SSB systematically overestimate the resiliency of stocks to fishing. If age-at-spawning is at least partially heritable, then intense fishing on younger ages may exert high levels of selection for early maturity with negative impacts on net reproductive effort and trait diversity.

Colonial Waterbird Predation on Juvenile Salmonids Tagged with Passive Integrated Transponders in the Columbia River Estuary: Vulnerability of Different Salmonid Species, Stocks, and Rearing Types

Abstract: Passive integrated transponder (PIT) tags implanted in Columbia River basin juvenile salmonids Oncorhyncus spp. were recovered from breeding colonies of Caspian terns Sterna caspia and double-crested cormorants Phalacrocorax auritus on Rice Island, a dredge spoil island in the Columbia River estuary. Tags were recovered to assess the relative vulnerability of different salmonid species, stocks, and rearing types to avian predators. We detected 50,221 PIT tags at the two bird colonies, mostly from juvenile chinook salmon O. tshawytscha and steelhead O. mykiss raised in hatcheries; 72% of the total tags were from the tern colony and 28% from the cormorant colony. Tagged steelhead smolts were more vulnerable to predation by both bird species than were yearling chinook salmon. More than 15% of PIT tags from steelhead smolts that were available in the estuary in 1998 were detected at the bird colonies compared with 2% of PIT tags from yearling chinook salmon. The greater vulnerability of steelhead may...

Predation and competition: the impact of fisheries on marine-mammal populations over the next one hundred years

Abstract: We discuss the potential for commercial fisheries to adversely impact ≥1 population of marine mammal by the end of the 21st century. To a large degree, patterns over the last 50 years regarding human population growth, success and failure in marine-fisheries management, and life history and status information on marine mammals are the basis for 6 predictions. First, annual worldwide landings of fish and shellfish by the end of the 21st century will be less than 80 million tons. Second, virtually all of the predictions regarding species composition and energy flow within a marine community, based on models developed to date with incomplete information on species abundance, food habits, genetic effects of fishing, and variability of predator food habits, will prove wrong on a decadal or longer time scale. Third, the most common type of competitive interaction between marine mammals and commercial fisheries will be that in which commercial fisheries adversely affect a marine-mammal population by depleting localized food resources without necessarily overfishing the target species of fish (or shellfish). Because of this, the number of extant populations and species richness of marine mammals will be reduced by the end of the 21st century, and coastal populations and species will be affected more negatively than will noncoastal species. Fifth, predator control programs designed to reduce local populations of marine mammals will be common without changes in existing forms of fishery management. Finally, protein from marine mammals will become a more important component of the human diet than it currently is.

Anomalous conditions in the south-eastern Bering Sea 1997: linkages among climate, weather, ocean, and Biology

Abstract: In 1997, the Bering Sea ecosystem, a productive, highlatitude marginal sea, demonstrated that it responds on very short time scales to atmospheric anomalies. That year, a combination of atmospheric mechanisms produced notable summer weather anomalies over the eastern Bering Sea. Calm winds, clear skies, and warm air temperatures resulted in a larger-than-normal transfer of heat to surface waters and the establishment of a shallow mixed layer. In spring, significant new production occurred below the shallow pycnocline over the Middle Shelf, depleting the subpycnocline nutrient reservoir that normally exists during summer. Following the depletion of nitrate and silicate from the system, a sustained (‡ 4 months) bloom of coccolithophores (Emiliania huxleyi) was observed ‐ a phenomenon not previously documented in this region. Summer Middle Shelf Domain copepod concentrations were higher for some species in 1997 than in the early 1980s. Warmer surface water and lack of wind mixing also changed the basic distribution of hydrographic regimes on the south-eastern shelf and altered the strength and position of fronts or transition zones where apex predators seek elevated food concentrations. The Inner Front was well inshore of its normal position, and adult euphausiids (the primary prey of short-tailed shearwaters, Puffinus tenuirostris )w ere unavailable at, and shoreward of, the front in autumn. High shearwater mortality rates followed the period of low euphausiid availability. Some, but not all, of these anomalous conditions re-occurred in 1998. These observations are another demonstration that the structure and function of marine ecosystems are intimately tied to forcing from the atmosphere. Alteration of climatological forcing functions, expressed as weather, can be expected to have large impacts on this ecosystem and its natural resources.

Survival of Juvenile Salmonids Passing through Bypass Systems, Turbines, and Spillways with and without Flow Deflectors at Snake River Dams

Abstract: Using yearling chinook salmon Oncorhynchus tshawytscha and steelhead O. mykiss tagged with passive integrated transponders (PITs), we estimated passage survival through bypass systems, turbines, and spill bays with and without flow deflectors at Snake River dams relative to survival of fish released into the tailrace below the dam. Actively migrating fish were collected and marked with PIT tags at Snake River dam smolt collection facilities. Groups of tagged fish were then released through hoses into different passage routes; releases were coincident with a tailrace release approximately 1–2 km below the dam. Relative survival was estimated by the use of tag–recapture models for paired releases from detections of individual PIT-tagged fish at juvenile collection or detection facilities at downstream dams. Detection sites included Little Goose, Lower Monumental, McNary, John Day, and Bonneville dams, depending on the release location and year. Standard errors of relative survival probability estim...

Spatially-explicit individual based modeling of marine populations: A review of the advances in the 1990s

Abstract: The utility of individual based models (IBMs) is that properties of ecological systems can be derived by considering the properties of individuals constituting them. Individual differences may be physiological, behavioral or may arise from interactions among individuals. The differences result in unique life histories, which when considered as a whole give rise to growth and size distributions that provide a measure of the state of the population. Early IBMs generally did not consider the effect of a spatially variable physical environment. Recent advances in ocean circulation models that include realistic temporal and spatial variation of currents, turbulence, light, prey, etc., have enabled IBMs to be embedded in model flow fields and for unique, sometimes behaviorally modified, Lagrangian trajectories to be computed. The explicit consideration of realistic spatial heterogeneity provides an additional factor that contributes to the differentiation among individuals, to variances in population s...

Characterizing diversity in salmon from the Pacific Northwest

Abstract: Information developed during recently completed evaluations of the status of seven species of anadromous Pacific salmonids (Oncorhynchus spp.) in the Pacific Northwest was used to characterize patterns of intraspecific diversity along three major axes: ecology, life history and biochemical genetics. Within the study area, the species' ranges, and therefore the number of distinct ecological regions inhabited differ considerably, with pink and chum salmon limited to the northern areas and chinook salmon and steelhead distributed over the widest geographic range. The species showed comparable differences in the patterns of life history and genetic diversity, with chinook and sockeye salmon and steelhead having the most major diversity groups and pink, chum and coho salmon having the least. Both life history and genetic diversity showed a strong, positive correlation with the extent of ecological diversity experienced by a species, and the correlation between the number of major genetic and life history groups within a species was even stronger (r=0.96; P<0.05). Departures from these general diversity relationships found in some species (especially sockeye and coho salmon and cutthroat trout) can be explained by different interactions with the freshwater environment and, for cutthroat trout, by the occurrence of substantial intrapopulational diversity in life history traits, a hierarchical level not considered in this study.

Biological enhancement at cyclonic eddies tracked with GOES thermal imagery in Hawaiian waters

Abstract: In November 1999, ship and satellite platforms were used to track, target and map the vertical and horizontal structure of two cyclonic eddies in the lee of Hawaii. Depth-integrated nitrate+nitrite levels within the photic zone of the eddy cores were 3- to 15- fold higher than those observed for control stations. The depth and magnitude of the deep chlorophyll maximum were significantly elevated in the more mature of the two eddies. HPLC analyses revealed that the enhanced chlorophyll was largely contributed by chromophyte microalgae. Modeled primary productivity rates were up to twofold higher at the stations within the eddies.

Interannual variability of boundary fluxes and water mass properties in the Gulf of Maine and on Georges Bank: 1993–1997☆☆☆

Abstract: Analysis of three years (October 1993–September 1996) of monthly mean current, temperature and salinity observations from moorings in the major Gulf of Maine (GOM) inflows off southwest Nova Scotia (C2) and in Northeast Channel (NECE) reveals some new features of the annual NECE cycles, including (1) a peak in near-surface ( 75 m) NECE inflow, followed by later episodes of enhanced cold, fresh inflow at C2 and shallow NECE. Generally, the flow rates at C2 and deep NECE were out of phase, with increased inflow at C2 (deep NECE) associated with reduced inflow at deep NECE (C2) and cooler, fresher (warmer,saltier) conditions at both sites. Freshwater transport anomalies to the Gulf are maximum in the surface layers and largely negative(positive) over the first(last) half of the measurements. The timing of these freshwater inflow variations is consistent with observed fluctuations in hydrographic measurements in the GOM and GB, which reached peak salinities in late 1994, then declined through 1995–1996. Oxygen isotope analysis suggests that almost all of the fresh water present on the central cap of GB in 1996 and early 1997 is of northern (Scotian Shelf) origin as opposed to 1994 and 1995 when Maine River Waters contributed 38 and 26%, respectively, to the freshwater (relative to 34.8) on the cap. A simple box model driven by observed changes in the boundary fluxes indicates that over the last half of the measurement period (April 1995–September 1996), the volumetric flow rate through the GOM increased by 10 5 m 3 s −1 (roughly 17% of the total transport, 5.83×10 5 m 3 s −1 ), and that increased freshwater fluxes in the surface layers at C2 and NECE produced a net decrease of 0.73 in the salinity of the outflow waters. Average volumetric transports at C2(NECE) were roughly twice(half) those observed in the late 1970s, but the total is consistent with climtological estimates. The net change in the freshwater fluxes exceeds the total climatological mean estimate. Examination of possible local and remote sources confirms that the origin of the 1996–1997 freshwater anomaly is in the northern Labrador Sea/Baffin Bay and results from exceptionally cold winters in the early 1990s. Analysis of a similar event in the early 1980s suggests their occurrence is part of a quasi-decadal climate signal which follows the North Atlantic Oscillation (NAO).

Stress induced by hooking, net towing, elevated sea water temperature and air in sablefish: lack of concordance between mortality and physiological measures of stress

Abstract: In a series of laboratory studies designed to simulate byeatch processes, sablefish Anoplopoma limbria were either hooked for up to 24 h or lowed in a net for 4 h and then subjected to an abrupt transfer to elevated sea water temperature and air. Mortality did not result from hooking or net towing followed by exposure to air, but increased for both capture methods as fish were exposed to elevated temperatures, rellecting the magnifying effect of elevated temperature on mortality. Hooking and exposure to air resulted in increased plasma corrisol and lactate concentrations, while the combination of hooking and exposure to elevated temperature and air resulted in encreased lactate and potassium concentrations. In fish that were towed in a net and exposed to air, cortisol, lactate, potassium and sodium concenrations increased, but when subjected to elevated temperature and air, ne further increases occurred above the concentrations induced by ter towing and air, suggesting a possible maximum of the physiological stress responise. The results suggest that caution should be exercised when using physiological measures to quantify stress induced by capture and exposure to elevated temperature and air, that altimately result in mortality, since the connections between physiological stress and mortality in bycatch precesses remain to be fully understood.

Characterizing population vulnerability for 758 species

Abstract: We investigate relationships between life history traits and the character of population dynamics as revealed by time series data. Our classification of time series is according to ‘extinction category,’ where we identify three classes of populations: (i) weakly varying populations with such high growth rates that long-term persistence is likely (unless some extreme catastrophe occurs); (ii) populations with such low growth rates that average population size must be large to buffer them against extinction in a variable environment; and (iii) highly variable populations that fluctuate so dramatically that dispersal or some other refuge mechanism is likely to be key to their avoidance of extinction. Using 1941 time series representing 758 species from the Global Population Dynamics Database, we find that, depending on the form of density dependence one assumes, between 46 and 90% of species exhibit dynamics that are so variable that even large carrying capacities could not buffer them against extinction on a 100-year time horizon. The fact that such a large proportion of population dynamics are so locally variable vindicates the growing realization that dispersal, habitat connectedness, and large-scale processes are key to local persistence. Furthermore, for mammals, simply by knowing body size, age at first reproduction, and average number of offspring we could correctly predict extinction categories for 83% of species (60 of 72).

Fishery Production and the Mississippi River Discharge

Abstract: There is strong circumstantial evidence worldwide that nutrient enriched riverine discharge enhances fishery production on adjacent continental shelves, and this appears to be the case with the Mississippi River where 70–80% of Gulf of Mexico fishery landings come from waters surrounding the Mississippi delta. Two major species groupings, estuarine dependent species (e.g., red drum, Sciaenops ocellatus; spot, Leiostomus xanthurus; and Atlantic croaker, Micropogonias undulatus) and coastal species, (e.g., king mackerel, Scomberomorus calvalla; Spanish mackerel, Scomberomorus maculatus; and bluefish, Pomatomus saltatrix) are most likely to be influenced by riverine discharge. While riverine enhancement of fishery production seems clear, the exact mechanisms through which this occurs are not. Because recruitment makes the greatest contribution to fish stock biomass, it is by enhancing recruitment that fishery production is influenced most. Waters influenced by the river discharge are a rich environm...

Habitat-specific distribution of Pacific ocean perch (Sebastes alutus) in Pribilof Canyon, Bering Sea

Abstract: Shelf edge canyons are well-known sites of enhanced biomass due to on-shore transport and concentration of zooplankton along their axes, both of which contribute to the high densities of nekton frequently found in these canyons. Using a combination of acoustics, trawling, and in situ observations with a remotely operated vehicle (ROV), the distribution of pelagic and demersal biota within Pribilof Canyon in the Bering Sea was examined in September of 1995 and 1997. Near-bottom acoustic scattering patterns in the 38kHz data showed high concentrations of biomass beginning around the 180m bottom depth contour and continuing to about 220m, which were presumed to be adult fish based on their target strength distributions. The 120kHz data also showed very strong scattering in the water column between 150 and 175m, which was absent from the 38kHz data, and therefore attributed mainly to zooplankton. The dominant taxa collected in bottom trawls and mid-water plankton tows were adult rockfishes (Pacific ocean perch, Sebastes alutus) and euphausiids (Thysanoessa spp.), respectively. In situ videos revealed dense aggregations of these rockfishes inhabiting a ‘‘forest’’ of attached sea whips, Halipteris willemoesi, during night deployments of the ROV, while areas with damaged sea whips had far fewer rockfish, and areas without this biotic habitat structure had no rockfish. During the day, the rockfishes were seen above the ‘‘forest’’, where they were apparently feeding on dense swarms of euphausiids. It appears that these rockfish utilize this predictable and abundant food resource in the canyon during the day and are associated with the sea whip habitat at night during periods of inactivity. More research is needed on these slowgrowing biotic habitats and how fishing activities in the Bering Sea and elsewhere may impact these habitats. # 2001 Elsevier Science Ltd. All rights reserved.

Stable isotope assessment of temporal and geographic differences in feeding ecology of northern fur seals (Callorhinus ursinus) and their prey.

Abstract: We investigated the feeding ecology and foraging location of migrating and nursing northern fur seal (Callorhinus ursinus) adult females and migrating juvenile males from the Pribilof Islands, Alaska, using carbon (δ13C) and nitrogen (δ15N) isotope analysis of fur seal skin and whole potential prey. Post-parturient and lactating females had mean δ15N values significantly (0.8‰) higher than pregnant, migratory females, and δ13C values that were not significantly different. Two opportunistically collected, migrating, nulliparous females had mean δ13C values 1.1‰ lower than migrating, pregnant females, and δ15N values that were not different. Pregnant, migratory females had mean δ13C values significantly (~1.5‰) higher than migratory juvenile males, and mean δ15N values significantly (~0.6–1.6‰) higher than migratory juvenile males. The exception was one group of juvenile males from St. Paul Island with mean δ15N values that were not significantly different from migrating females. The mean δ15N values of pregnant females indicate they were feeding at a higher trophic level than juvenile males during migration. The higher mean δ13C values for pregnant females suggest they were feeding coastally during the spring migration, while juvenile males and nulliparous females were feeding offshore. The higher δ15N values for post-parturient, lactating females over migrating, pregnant females point to either a trophic shift in diet over time, or a more likely 15N-enrichment due to negative nitrogen balance caused by the nutritional stress of lactation and the feeding/fasting regime experienced by females. Similar mean δ13C values for migrating and breeding-season females indicate that both groups were feeding in coastal, on-shelf domains during their respective time periods. Similar mean δ15N values for nulliparous and pregnant females indicate they were feeding at similar trophic levels despite indications of feeding in separate ecosystems during migration. Using a δ15N shift of 2–3‰ per trophic level, we made general inferences about the trophic levels at which northern fur seals were feeding. The interpretation of our δ15N data indicates that migrating pregnant females, lactating females and the majority of migrating juvenile males consumed prey with mean δ15N values between 14.2‰ and 15.2‰, 15.1‰ and 16.1‰, and 13.6‰ and 14.6‰, respectively. Probable fur seal prey was analyzed as well. Walleye pollock showed progressive 15N and 13C-enrichments with age. Mean δ15N and δ13C values of 3- to 4-year-old fish were ~6.0‰ and 1.1‰ higher, respectively, than values for 0-age pollock. Atka mackerel also showed isotopic enrichment with age. The δ15N and δ13C values of large fish were 0.8‰ and 0.3‰ higher, respectively, than values for smaller fish.

Characterization of beaked whale (ziphiidae) and sperm whale (physeter macrocephalus) summer habitat in shelf‐edge and deeper waters off the northeast u. s.

Abstract: Sperm whales (Physeter macrocephalus) and beaked whales (Mesoplodon spp. and Ziphius cavirostris) are deep-diving cetaceans that frequent shelf-edge and Gulf Stream waters off the northeast U. S. coast. Sighting data collected during seven summer (1990, 1991, 1993, and 1995–1998) shipboard surveys were analyzed using a geographic information system to determine habitat use based on bathymetric and oceanographic features. Although sighting rates were lower for beaked whales, both taxa occupied similar habitats. Beaked whales were concentrated at the colder shelf edge, whereas sperm whales were associated with warmer off-shelf water. Mean sighting rates for both taxa were higher in canyon features, but only beaked whale sighting rates were significantly different between canyon and non-canyon habitat (Wilcoxon signed rank test P= 0.007). Within the shared habitat, the two taxa were separated at fine-scale based on oceanographic features.

Effects of ration on somatotropic hormones and growth in coho salmon

Abstract: We examined the response of growth hormone (GH), total plasma insulin-like growth-factor I (IGF-I), and growth rate to a change in ration in coho salmon. Tanks of individually tagged fish were placed on high, medium, or low ration, and sampled every 2 weeks for 8 weeks to create a range of growth rates. Some fish received non-lethal blood draws, while others were sampled terminally. Plasma IGF-I levels were higher in high ration fish than in low ration fish from 4 weeks after the beginning of experimental diets to the end of the experiment. GH levels were low and similar in all fish after changing rations, except for the fish in the low ration group at week 2. IGF-I was strongly correlated with specific growth rate in weight in terminally sampled fish after 4 weeks. GH did not correlate with growth rate or IGF-I levels. Growth parameters (length, weight, specific growth rates in weight and length, and condition factor) responded to ration. Serial sampling reduced growth rates and hematocrit, but did not change hormone levels. This study shows that IGF-I responds to changed rations within 2-4 weeks in salmonids.

Impact of algal research in aquaculture

Abstract: Algal aquaculture worldwide is estimated to be a $5-6 billion U.S. per year industry. The largest portion of this industry is represented by macroalgal production for human food in Asia, with increasing activity in South America and Africa. The technical foundation for a shift in the last half century from wild harvest to farming of seaweeds lies in scientific research elucidating life histories and growth characteristics of seaweeds with economic interest. In several notable cases, scientific breakthroughs enabling seaweed-aquaculture advances were not motivated by aquaculture needs but rather by fundamental biological or ecological questions. After scientific breakthroughs, development of practical cultivation methods has been accomplished by both scientific and commercial-cultivation interests. Microalgal aquaculture is much smaller in economic impact than seaweed cultivation but is the subject of much research. Microalgae are cultured for direct human consumption and for extractable chemicals, but current use and development of cultured microalgae is increasingly related to their use as feeds in marine animal aquaculture. The history of microalgal culture has followed two main paths, one focused on engineering of culture systems to respond to physical and physiological needs for growing microalgae and the other directed toward understanding the nutritional needs of animals-chiefly invertebrates such as mollusks and crustaceans-that feed upon microalgae. The challenge being addressed in current research on microalgae in aquaculture food chains is to combine engineering and nutritional principles so that effective and economical production of microalgal feed cultures can be accomplished to support an expanding marine animal aquaculture industry.

Killer whale predation on sperm whales: observations and implications

Abstract: In October 1997 we observed a herd of approximately 35 killer whales (Orcinus orca) attack a pod of nine sperm whales (Pbyseter macrocephalus) 130 km off the coast of central California. During the four hours we watched, adult female killer whales, including some with calves, attacked in waves of four to five animals in what was apparently a “wound and withdraw” strategy. Adult male killer whales stood by until the very end when one charged in and quickly killed a seriously wounded sperm whale that had been separated from the group. The sperm whales appeared largely helpless: their main defensive behavior was the formation of a rosette (“marguerite”-heads together, tails out). When the killer whales were successful in pulling an individual out of the rosette, one or two sperm whales exposed themselves to increased attack by leaving the rosette, flanking the isolated individual, and leading it back into the formation. Despite these efforts, one sperm whale was killed and eaten and the rest were seriously, perhaps mortally, wounded. We also present details of two other encounters between sperm whales and killer whales that we observed. Although sperm whales, because of various behavioral and morphological adaptations, were previously thought to be immune to predation, our observations clearly establish their vulnerability to killer whales, We suggest that killer whale predation has potentially been an important, and underrated, selective factor in the evolution of sperm whale ecology, influencing perhaps the development of their complex social behavior and at-sea distribution patterns.

Physical-biological coupling in the California Current during the 1997–99 El Niño-La Niña Cycle

Abstract: The rapid transition from strong El Nino to strong La Nina conditions in the equatorial Pacific in 1998 was accompanied by considerable environmental variability in the southern California Current System (CCS) The evolution of this transition in the CCS is investigated based on hydrographic and biological data collected on 25 cruises over a 45-month period (February 1996 to October 1999) The El Nino period was characterized by high steric heights and a deep nutricline in the coastal regions, which effectively limited biological production This was followed by a period of increased cross-shore dynamic height gradients, a significant shoaling of the nutricline, and a dramatic rebound in primary and secondary production The observed physical and biological response in the CCS is remarkably similar to that observed in the tropical Pacific, but with a lag of several months