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Evidence-based guidelines represent the highest level of scientific evidence to identify best practices for clinical/public health. However, the availability of guidelines do not guarantee their use, targeted knowledge translation strategies and tools are necessary to help promote uptake. Following publication of the 2019 Canadian Guideline for Physical Activity throughout Pregnancy, the Get Active Questionnaire for Pregnancy, and an associated Health Care Provider Consultation Form for Prenatal Physical Activity were developed to promote guideline adoption and use amongst pregnant individuals and health care providers. This paper describes the process of developing these tools. First, a survey was administered to qualified exercise professionals to identify the barriers and facilitators in using existing prenatal exercise screening tools. A Working Group of researchers and stakeholders then convened to develop an evidence-informed exercise pre-participation screening tool for pregnant individuals, building from previous tool and survey findings. Finally, end-user feedback was solicited through a survey and key informant interviews to ensure tools are feasible and acceptable to use in practice. The uptake and use of these documents by pregnant individuals, exercise, and health care professionals will be assessed in future studies. Novelty: Evidence supports the safety/benefits of exercise for most pregnant individuals; however, exercise is not recommended for a small number of individuals with specific medical conditions. The Get Active Questionnaire for Pregnancy and Health Care Provider Consultation Form for Physical Activity during Pregnancy identify individuals where prenatal exercise may pose a risk, while reducing barriers to physical activity participation for the majority of pregnant individuals.

Manual collection of accurate phenology data is time-consuming and expensive. In this study, we investigate whether repeat colour digital photography can be used (1) to identify phenological patterns, (2) to identify differences in vegetation due to experimental warming and site moisture conditions, and (3) as a proxy for biomass. Pixel values (RGB) were extracted from images taken of permanent plots in long-term warming experiments in three tundra communities at a high Arctic site during one growing season. The Greenness Excess Index (GEI) was calculated from image data at the plot scale (1 × 1 m) as well as for two species, Dryas integrifolia and Salix arctica. GEI values were then compared to corresponding field-based phenology observations. GEI and Normalized Difference Vegetation Index (NDVI) values from a paired set of true colour and infrared images were compared with biomass data. The GEI values followed seasonal phenology at the plot and species scale and correlated well with standardized observations. GEI correlated well with biomass and was able to detect quantitative differences between warmed and control plots and the differences between communities due to site-specific moisture conditions. We conclude that true colour images can be used effectively to monitor phenology and biomass in high Arctic tundra. The simplicity and affordability of the photographic method represents an opportunity to expand observations in tundra ecosystems.

Interannual growth variations were compared among neighbouring populations of lake sturgeon (Acipenser fulvescens) and white spruce (Picea glauca), white pine (Pinus strobus), and red pine (Pinus resinosa). Measures of growth were obtained by removing long-term trends from widths of rings in the hard tissues of both aquatic and terrestrial organisms and assembling these measures into growth chronologies. Interannual growth variations were negatively correlated (r) between sturgeon and nearby tree population chronologies for those fish populations that displayed strong interseries correlation (mean r). The three sturgeon population chronologies developed from individuals that displayed the lowest interseries correlation coefficients failed to display significant correlation with tree growth. The results of this investigation indicate that the negative relationships between fish and tree growth may be related to annual fluctuations in air temperature. In general, fish population chronologies displayed positive correlation with measures of air temperature during the current season of growth, while tree population chronologies displayed negative correlation with air temperatures from either the current or the previous season of growth.

Mitochrondrial DNA analysis resolved many previously unanswered questions concerning the phylogeny of the lamprey genus Lampetra (comprising the subgenera Entosphenus, Lethenteron, and Lampetra). A total of 735 base pairs were sequenced from the cytochrome b and NADH dehydrogenase subunit 3 (ND3) genes in 11 lamprey species. With the exception of L. (E.) hubbsi from California, species of the Entosphenus subgenus formed a tight-knit clade that was very distinct from the other two subgenera. Lampetra hubbsi clustered with species of the Lampetra subgenus from the west coast of North America (L. ayresii and L. richardsoni) whereas species of the Lampetra subgenus from Atlantic drainages, namely the North American L . aepyptera and European L. fluviatilis, formed a third cluster. A fourth cluster included two species from the Lethenteron subgenus (L. japonica and L. appendix). Inclusion of published data from a third Lethenteron species, L. zanandreai, showed it to group with the L. (L.) fluviatilis lineage rather than with the other two Lethenteron species. Within each subgenus, members of paired and satellite species were closely related to one another (e.g., L. japonica and L. appendix) or were genetically indistinguishable (e.g., L. ayresii and L. richardsoni). Using rates of molecular evolution estimated in other fish taxa, these genetically indistinguishable species diverged less than 70 000 years ago.

The feasibility of stable oxygen and carbon isotope ratio (δ18O and δ13C) analyses in sagittal otoliths of sockeye salmon (Oncorhynchus nerka) was tested by analyzing the seasonal and annual otolith zones of 44 samples collected from different localities in the northeast Pacific coast. The δ18O and δ13C values of these otoliths ranged from -14.23 to +1.62‰ and from -15.18 to -3.17‰, respectively. The δ18O variations can be divided into two stages from freshwater (-14.2 to -2.5‰) to marine (-2.5 to +1.6‰) that were consistent with the life history of sockeye salmon from juvenile to adult stages. The transition occurred after age 1, during which the timing of seaward migration of smolts was different. The marine component of the isotope variation in sockeye salmon otoliths (ages > 2) was uniform but showed a consistent and strong shift towards oceanic changes around 1996. Thus, δ18O and δ13C values of otoliths can be potentially used as a chemical tracer in population identification, and their marine portions can be used in the study of ocean environmental changes.

Wild and hatchery-reared coho salmon (Oncorhynchus kisutch) from streams and rivers that flow into the Strait of Georgia are caught in the Strait of Georgia and off the west coast of Vancouver Island. The percentage of coho caught in either of these two areas varies from year to year. The variation is associated with the flow of freshwater from the Fraser River and became more extreme in the 1990's. In four of eight years in the 1990's and in the past three years, most coho have been caught outside the Strait of Georgia. The dramatic decline in the sport catch in the Strait is related to ocean conditions in the Strait. The change in ocean conditions is related to an increase in the number of days of zonal (westerly) winds in October, November, and December and to an increase in relative sea level height. The climate change about 1989 that affected the pattern of winter winds and the circulation in the Strait of Georgia was associated with changes in other global climate indices, demonstrating the impact that global climate events can have on the dynamics of regional salmon stocks.

Large fluctuations in the trends of Pacific salmon production in this century have been linked to trends in climate in the Pacific that are in turn associated with climate trends throughout the Northern Hemisphere. The close correspondence in the persistence of climate trends and the synchrony of the changes is evidence that a common event may cause the regime shifts. The trends or regimes can be characterized by stable means in physical data series or multiyear periods of linked recruitment patterns in fish populations. The regime concept is important in fisheries management because the natural shifts in abundance may be large and sudden, requiring that these natural impacts be distinguished from fishing effects. An equally important consideration is that biological and physical mechanisms may change when regimes shift, resulting in conditions that may not be characterized in the earlier part of the data series. Fluctuations in Pacific salmon abundance in this century were synchronous with large fluctuations in Japanese sardine abundance, which can be traced back to the early 1600's. The synchrony in the fluctuations suggests that Pacific salmon abundance may have fluctuated for centuries in response to trends in climate. The concept of regimes and regime shifts stresses the need to improve our understanding of the mechanisms that regulate the dynamics of fish and their ecosystems.

The spatial and temporal distribution and relative abundance of juvenile lake sturgeon (Acipenser fulvescens) and benthic macroinvertebrates were examined in the Mattagami and Groundhog rivers, tributaries of the Moose River in northern Ontario, Canada. Relative density and diversity of the benthic fauna were low, the most common taxa being Ablabesmyia sp. (Diptera) and Hexagenia sp. (Ephemeroptera). Benthic organisms were most abundant in substrate dominated by sand and clay. An appreciable portion of the riverbed was strewn with wood chips and was particularly depauperate of macrobenthos. Lake sturgeon foraged exclusively on the benthos, especially taxa of Ephemeroptera, Diptera, and Trichoptera. Hexagenia was the only prey species in greater density in sturgeon stomachs than in the benthos. The largest concentration of juvenile lake sturgeon was found adjacent to substrate dominated by sand and clay. Gillnet catches of lake sturgeon suggest that they are more active at night, which may enhance their foraging success. In these northern rivers, the trophic status of juvenile lake sturgeon is marginalized by an impoverished food supply, in part the consequence of habitat loss resulting from anthropogenic activities.

Fishways have traditionally been designed to provide safe passage for jumping fish and only recently have nonjumping species been considered. Concern over dwindling populations of lake sturgeon, Acipenser fulvescens, has focused attention on fishway designs that accommodate its swimming abilities. The objective of this study was to derive a model that relates swimming endurance of lake sturgeon to length and flow characteristics of fishways. Endurance at sustained and prolonged swimming speeds (those maintainable for more than 20 s) increased with water temperature but was independent of temperature at higher burst speeds. Endurance increased with total length at all swimming velocities. Swimming performance of lake sturgeon, relative to body length, is inferior to that of most salmonids, particularly at burst speeds. Fishway designers need to consider swimming ability, space requirements, and behavior of lake sturgeon to ensure that they can ascend potential migratory obstacles safely.

High-resolution vertical profiles of salinity, temperature, fluorescence, and nutrients (NO3 and SiO4) were taken along a transect in the central Strait of Georgia, British Columbia. The Fraser River discharge increased rapidly over 4 days and then decreased over the following 3 days (June 16-19, 1991). The thickness and extent of the estuarine plume increased as a response to the increased river discharge. As the estuarine plume flowed seaward, the nutricline (NO3) became shallower and broader, resulting in an increase in NO3 in the euphotic zone. Entrainment of NO3 may explain the increase in NO3 in the surface layer, and the amount of NO3 entrained was estimated to be 5-10 times higher than river-borne NO3. The utilization of entrained nutrients increased Chl a concentrations and primary production to levels comparable with spring bloom values. Our results clearly demonstrated for the first time that entrainment of nutrients and phytoplankton production in the central Strait of Georgia are closely coupled to fluctuations in the Fraser River discharge as the estuarine plume moves seaward. The timing and magnitude of the May-June freshet could control the entrainment of nutrients and thus maintain high primary productivity in late spring - early summer.

The abundance of Fraser River sockeye salmon (Oncorhynchus nerka) stocks was low in the 1960s, increased to high levels in the 1980s, and possibly entered a period of low abundance in recent years. The abundance changes of the combined stocks can be separated into productivity regimes that correspond to changes in climate trends. The most distinct change occurred when there was a major change in the climate over the Pacific Ocean in the winter of 1976-1977. The existence of natural shifts in abundance trends means that the high returns that occur during periods of high productivity would not be expected to occur during the low-productivity periods. The response of Fraser River sockeye to climate changes may be a specific example of a more general response by a number of species of fishes in the Pacific and perhaps in other oceans. Because the shift from one regime to the other occurred quickly in the 1970s, future shifts could also occur quickly. It is necessary to detect natural shifts in productivity when attempting to manage fishing impacts to ensure that economic expectations are sound and that overfishing does not occur.

On a obtenu des informations sur la lamproie de l'est, Lampetra appendix, et sur son habitat physique au cours de l'ete, dans 10 cours d'eau du second ordre un peu partout dans l'aire de distribution geographique de cette espece. On a mesure la densite des larves et plusieurs descripteurs de la taille des larves, de la composition, de la distribution granulometrique, de la conductivite hydraulique, de la porosite, de la teneur en matieres organiques, de la vitesse du courant et de la profondeur de l'eau, a un certain nombre d'endroits dans chaque cours d'eau. Des analyses par regression multiple indiquaient l'existence d'une correlation positive entre la densite des larves et le pourcentage de sable mi-fin et de matieres organiques dans le substrat. La densite des larves etait normalement elevee lorsque la plage des tailles etait grande et que les petites lamproies etaient relativement abondantes, ce qui reflete des exigences semblables relatives a l'habitat chez les categories d'âges, ainsi que la dynamique entre le recrutement et la mortalite chez les larves. On a observe ces resultats dans 10 cours d'eau. Dans trois cours d'eau, la densite des larves etait etroitement liee au sable mi-fin et aux matieres organiques; dans deux cours d'eau, la densite accrue des larves etait moins evidente; tandis que dans cinq cours d'eau, l'abondance etait etroitement reliee au sable mi-fin et aux matieres organiques. Les autres variables n'avaient aucun effet significatif sur la densite des larves. On examine les importantes variables de l'habitat dans le contexte de l'ecologie de l'espece.

On a etudie des changements saisonniers et relies a la taille, observes dans la composition des constituants immediats et la teneur energetique des esturgeons jaunes d'une population de la portion nord de l'aire de repartition geographique de cette espece. Le facteur de condition augmentait en fonction de la longueur totale de ce poisson, sans presenter de variations saisonnieres. De meme, on a note, dans tout l'organisme et les muscles, une augmentation en fonction de la longueur des teneurs en eau, en proteines, en lipides et en matieres inorganiques, ainsi que de la teneur energetique. En general, les valeurs de chaque constituant immediat et de la teneur energetique pour les esturgeons d'une taille donnee ne variaient pas entre juin et octobre, mais elles etaient differentes en mars; les teneurs en lipides et proteines variaient en raison inverse de la teneur en eau, exprimee en pourcentage du poids corporel total. La valeur de l'indice hepatosomatique diminuait en fonction de la longueur totale, mais ces valeurs ne presentaient pas de differences entre juin et octobre, et en mars, elles etaient inferieures. Les teneurs relatives en eau, en proteines et en matieres inorganiques du foie diminuaient alors que les teneurs lipidiques et energetiques augmentaient en fonction de la longueur totale. Pour des esturgeons jaunes d'une longueur donnee, les teneurs relatives lipidiques et energetiques du foie etaient a leur plus bas en mars, alors que la teneur lipidique etait a son maximum en juillet, soit l'inverse de ce qu'on a observe pour les teneurs en proteines et en eau.

River lamprey (Lampetra ayresi) enter the Strait of Georgia from the Fraser River and feed almost exclusively on Pacific herring (Clupea harengus) and salmon (Oncorhynchus spp.). Although the major prey of river lamprey is Pacific herring, the greater effect of lamprey predation was on the populations of chinook (O. tshawytscha) and coho (O. kisutch) salmon. In 1990 and 1991, river lamprey killed a minimum of 20 million and 18 million chinook salmon, respectively, and a minimum of 2 million and 10 million coho salmon in the same years. In 1991, river lamprey in the Fraser River plume killed an equivalent of approximately 65 and 25% of the total Canadian hatchery and wild production of coho and chinook salmon, respectively. These estimates are probably low because river lamprey also feed in other areas and the abundance estimates are conservative. These high mortality rates indicate that river lamprey predation must be considered as a major source of natural mortality of chinook and coho salmon in the Strait of Georgia.

We determined the effects of temperature (8 and 16 °C) and water concentrations of potassium (0.01–3.4 mmol/L), sodium (0.4–3.0 mmol/L), and calcium (0.3–2.9 mmol/L) on the dynamics of137Cs in rainbow trout (Oncorhynchus mykiss). Trout were fed food labelled with137Cs, and137Cs retention was monitored by whole body gamma counting (70 d). Assimilation of137Cs did not vary significantly over the range of concentrations of K+, Na+, and Ca2+employed, with an average value of 65 ± 3% (mean ± SE). The elimination of137Cs was significantly affected by K+, with the elimination rate constant of trout held at the highest K+concentration (0.021 ± 0.001 d−1at K+of 3.4 mmol/L) roughly double that observed in trout at lower K+(0.011 ± 0.001 d−1at K+≤ 0.3 mmol/L). Elimination of137Cs was also significantly affected by temperature, with the increase in elimination rate over the range of 8 and 16 °C corresponding to a Q10of ≈1.7. Although the effect of K+on accumulation of137Cs in trout was statistically significant, this effect, by itself, can explain only a small fraction of the broad range of137Cs concentration ratios reported for wild fish.

Otolith microstructure exhibited some characteristic differences between hatchery-reared and wild chinook salmon (Oncorhynchus tshawytscha) from the Cowichan River. Daily growth increments that formed in the otoliths of the hatchery-reared chinook salmon after exogenous feeding were more regular in width and contrast than those in the otoliths of wild chinook salmon. In addition, otoliths from hatchery-reared individuals frequently produced a check when the fish were released from the hatchery. Eighty-nine percent of a sample of 67 chinook smolts that had been coded-wire tagged in hatcheries and later captured in the Strait of Georgia were correctly identified as originating from hatcheries based on otolith microstructure. These tagged fish originated from at least 17 different hatcheries, indicating that the method could be used to identify chinook salmon originating from other hatcheries.

Agnathans are the only vertebrates without a thymus, yet lampreys possess putative lymphocytes whose responses parallel those of T cells in gnathostomes. The phylogenetically conserved Thy-1 antigen is often associated with the thymus, thymocytes, and T cells. An immunohistochemical study, using commercial anti-rat brain Thy-1.1 antiserum and an immunoperoxidase procedure (peroxidase anti-peroxidase) was conducted to identify any Thy-1 antigenicity in various tissues of larval sea lampreys (Petromyzon marinus L.) lightly fixed in a chilled aldehyde-based solution. The primary focus of the experiment was to discover if Thy-1 immunoreactivity was associated with haemopoietic sites and (or) leukocytes. This technique permitted conventional histological sectioning, preserved tissue architecture, and retained Thy-1 antigenicity. In the haemopoietic typhlosole, the peripheral stroma and many lymphocyte-like cells stained intensely, as did similar cells in the opisthonephros, intestinal venous sinus, and liver. Immunoreactivity in the pharynx was evidenced only by weakly staining stroma in small labyrinthine subdermal foci dorsal and ventral to some external gill openings. It is proposed that if functions analogous to thymic activities exist in the larval lamprey, the typhlosole is the most likely site for their discovery.

We identified years of anomalously high and low discharge from the Fraser River and compared these years with indices of anomalously high and low production of Pacific salmon (Oncorhynchus spp.) and Pacific herring (Clupea pallasi). For chinook (O. tshawytscha) and coho salmon (O. kisutch), we found that brood years that went to sea in a year when the Fraser River discharge was very high compared with the previous year virtually never had an index of production that was higher than the previous year. Similarly, brood years that went to sea in a year when the Fraser River discharge was very low compared with the previous year almost never had an index of productivity that was lower than the previous year. The analysis identified a weaker association between extreme discharge anomalies and chum salmon (O. keta) production. A close association was not found between extreme discharge anomalies and pink salmon (O. gorbuscha), sockeye salmon (O. nerka), or herring production. The relationships identify a connection between annual fluctuations in river flow and production of some marine fishes and may be of use in forecasting abundance changes.

After 11 mo in the laboratory, significantly more sea lamprey, Petromyzon marinus, larvae from the Chippewa River, Michigan, metamorphosed in an ambient temperature regime (3 ± 2 animals∙tank−1) compared with a fixed 21 °C temperature (0 animals); photoperiod and food deprivation did not have detectable effects on the incidence of metamorphosis. Metamorphosing animals in our laboratory study were significantly smaller in size (length and weight) and had a lower condition factor (CF) than animals from the same population that metamorphosed a year earlier under field and shorter term laboratory conditions. We also predicted, using criteria of 120 mm, 3.0 g, and a CF of 1.50, that 12 and 14% of the animals in the ambient and fixed temperature regimes, respectively, would metamorphose. Our prediction for the ambient temperature did not differ significantly from observed (11%). We suggest that larvae in landlocked populations of sea lamprey that are at least 120 mm long, weigh 3.0 g, and have a CF of 1.50 or greater in the fall can be predicted to metamorphose the following summer. Furthermore, our data show that low temperature during the winter followed by rising temperature in the spring is the primary environmental cue initiating metamorphosis in sea lamprey.

The incidence of metamorphosis of larval sea lamprey, Petromyzon marinus, was strongly affected by water temperature but not photoperiod. In a 1991 experiment, the development of metamorphosing animals in 13 °C water was retarded about 1 mo relative to animals metamorphosing at 21 °C and to a population from the Chippewa River, Michigan; the minimum length, weight, and condition factor (CF) of metamorphosing experimental animals were 117 mm, 2.8 g, and 1.50, respectively, and only 4% metamorphosed at 13 °C and 18.9% at 21 °C. In 1992, with a population from the Great Chazy River, New York, 66% of the animals at 13 °C and 84% at 21 °C metamorphosed. The higher incidence of metamorphosis in 1992 is partly related to the use of larvae that were larger than the minima established in 1991. We predicted, using criteria defined below, that 74 and 72% of the animals at 13 and 21 °C, respectively, would metamorphose. Our predictions were consistent with observations at 13 °C and for five of seven replicate tanks at 21 °C. We suggest that a presumptive metamorphosing sea lamprey in landlocked populations should be at least 120 mm long, weigh 3.0 g, and have a CF ≥ 1.50 and that these criteria must be used in conjunction.

From 1976 to 1978 there was a change in the climate over the North Pacific Ocean. The Aleutian Low intensified and there was a warming of the sea surface adjacent to North America and a cooling offshore. Associated with this change was a period of exceptional fish production. Strong year classes and above-average survival occurred for many commercially important species all along the west coast of Canada and the United States. Trends in total salmon catches increased primarily from increased salmon production in Alaska. Some stocks of maturing pink (Oncorhynchus gorbuscha), coho (O. kisutch), and chinook salmon (O. tshawytscha) also had above-average growth in 1977. A majority of commercially important nonsalmon species that spawned from California to the Bering Sea and have a wide range of life history types also had exceptionally strong year classes from 1976 to 1978. The exceptional survival appears to be related to improved ocean productivity caused by changes in the intensity of the Aleutian Low.

Hypolimnetic trophic interactions were examined among lake trout (Salvelinus namaycush), cisco (Coregonus artedi), zooplankton, and macroinvertebrates in six northwestern Ontario lakes varying sevenfold in conductivity. Faster growth and larger body size of lake trout in high-conductivity lakes were associated with larger meal sizes, earlier entry of cisco into their diet, and consumption of relatively few, large-bodied prey. Cisco preyed on zooplankton and macroinvertebrates. Cisco were abundant, large bodied, and fast growing in high-conductivity lakes. In one low-conductivity lake (Greenwich Lake), lake trout were 12 times as abundant as cisco whereas in all other lakes, lake trout to cisco ratios were ~ 1:1 or less regardless of conductivity. In Greenwich Lake, lake trout consumed large quantities of age-0 cisco and Mysis relicta, which was associated with "top-down" trophic structuring. Food web analyses strongly suggest that in Greenwich Lake the high abundance of piscivores resulted directly in a low abundance of planktivores and indirectly in a large-bodied zooplankton community and planktivores with rapid growth rates.

Model simulations revealed that wind mixing was the dominant physical mechanism that added nitrate to the surface layer and subsequently enhanced primary productivity in the Strait of Georgia. Simulations of high Fraser River runoff showed that the enhanced stability of the water column in the vicinity of the riverine plume made wind mixing of nutrients into the surface layer more difficult. We propose that this increase in stability results in an earlier onset of the spring bloom in regions influenced by Fraser River runoff. During the summer, an increase in the buoyancy of surface water due to the freshwater plume reduces nitrate concentration in the surface layer and thereby limits primary production in the plume area. The reduced impact of wind events on nitrate fluxes is the result of a greater energy requirement to break down the more buoyant surface layer. Results indicate that during the fall, when light is again limiting and surface nitrate concentrations increase due to wind mixing by fall storms, the freshwater runoff from the Fraser River results in a more stable water column (similar to the spring situation) in the southern Strait, resulting in the potential for a fall bloom.

Sex ratios were determined for 20 populations of southern brook lamprey larvae, Ichthyomyzon gagei, collected from throughout much of their range in the southeastern United States. Ratios varied between 9 and 49% males. Differential mortality was an unlikely factor, as sex ratios were similar among age groups within each population. Environmental sex determination is suggested. Sex ratio varied with growth (expressed as length of larvae at specific ages), larval density, pH, and annual mean temperature of the natal stream. Generally, under conditions promoting rapid growth, the percentage of males varied directly with density and inversely with temperature. Where growth was slow, the percentage of males declined as larval density increased, the response being less at low than at high pH. Temperature had little effect when larval growth was slow. The percentage of males declined when growth was rapid under otherwise similar environmental conditions.

The anadromous parasitic Pacific lamprey (Lampetra tridentata) does not feed during metamorphosis or its spawning migration. To assess the utilization of body reserves, we compared the compositions of an adult lamprey held for 2 yr without food, recently metamorphosed lampreys, and lampreys starved for 6 mo. Moisture was higher and soluble ash and lipid levels were lower in tissue of the 2-yr-starved than in metamorphosed lampreys (2.67 and 3.39 kj∙g−1, respectively). Fatty acid profiles of 2-yr-starved and metamorphosed lampreys were qualitatively similar except for the presence of 15:0 in the latter. Substantially lower levels of 14:0 and 16:1 n7 and higher levels of polyunsaturated fatty acids occurred in starved lampreys. Changes in composition of lampreys starved for 6 mo were similar to changes between the 2-yr-starved and metamorphosed lampreys. Maintenance energy in a normalized 1-g lamprey starved for 6 mo was derived from catabolism of 71% lipid and 29% protein; total loss was 2.56 kJ or 49% of the original energy. The ability to survive extended periods on endogenous reserves, which may have allowed L. tridentata to survive past environmental catastrophes, allows it to migrate considerable distances to spawning areas in the headwaters of rivers.

Nitrogen and energy loss in fecal and nonfecal excretions by lake trout, Salvelinus namaycush (171–268 g), varied directly with dietary protein (40 and 50% dry weight) and inversely with lipid (10 and 20%) among four test diets. Diets high in lipid increased dry matter digestibility resulting in reduced nitrogen and energy loss in feces. NH3-N constituted 74.0–93.0% of total N excreted in fasted (4–12 d) and fed trout, while urea-N constituted 4.6–17.8% of total N. Excretion of urea-N was high in fish fed the high-lipid diet, particularly when dietary protein was also high. Total N and NH3-N excretion rose to peak values between 4 and 12 h after feeding and thereafter declined to prefeeding levels by 24 h. Urea-N excretion rates varied significantly following ingestion of all but one (50% protein, 20% lipid) test diet, reaching peak values between 4 and 12 h. In fasted fish, total N and NH3-N excretions were significantly low and failed to show a daily pattern; the urea-N excretion rate was significantly high compared with fish fed diets 1, 2, and 3 and followed a daily pattern of change. On average, a larger proportion (13–25%) of food energy is lost through nitrogenous excretion than in the feces (8–22%).

We present statistical models for estimating the true age distribution of a population, based on multiple readings from individual fish. There are two steps to this process. The first involves estimating a classification matrix that defines the probability of assigning an age a to a fish when its true age is b. Since true age is unknown, we require an assumption related to ageing error bias; we assume that the true age is the most probable value for the observed age. True age proportions, or alternatively, true ages of fish in the sample are then estimated in the second step. Our methods allow us either to conduct both steps simultaneously or to estimate true age proportions from a previously estimated classification matrix. We illustrate our methods with data on walleye pollock (Theragra chalcogramma). We recommend that multiple independent readings be obtained for a subset of structures in future ageing studies and that ageing error be considered in subsequent analyses. Sample sizes must be increased with increasing ageing error to achieve a specified precision in estimates of true age proportions.

Stomach contents from first-feeding larval sablefish (Anoplopoma fimbria) comprised mainly calanoid copepods. Along the west coast of Vancouver Island, these copepods were the dominant zooplankton at the depth that sablefish larvae developed. We propose that strong year-classes in sablefish populations occur when there is exceptional production of copepods. The periods of exceptional copepod production appear to be correlated with climate and ocean conditions.

Sea lamprey (Petromyzon marinus) larvae were individually marked with subcutaneous injections of latex dye and maintained in the laboratory from June 1988 to February 1989 at tank densities of 10, 50, and 100 larvae per 0.3 m2 of substrate. Growth, measured as change in total length and weight, varied widely among individuals: change in length during a 3-month period differed by as much as 17.0 mm within one tank of 10 larvae. Despite individual variation, growth decreased significantly with increasing density: the mean increase in length (± standard error) over the 8-month period was 17.3 ± 3.0, 4.3 ± 1.5, and −1.4 ± 1.0 mm at low, medium, and high density, respectively. The initial length or the sex of an individual at the end of the experiment had little or no effect on growth. Mortality was negligible (1.6%), and could not be significantly correlated with density, size, or sex. The overall sex ratio was 33% male, and did not vary significantly with tank or density.

Histological techniques were used to study adults of a single population of the brook lamprey, Lampetra richardsoni, in Morrison Creek, Vancouver Island, British Columbia, to establish whether there are any differences between the internal morphology of a "silver" variety (L. r. var. marifuga) and that of the nonparasitic variety (L. richardsoni). The results of the study support the view of two life-history types in this creek. When L. richardsoni is sexually mature and has an atrophied intestine and sparse haemopoietic tissue, most L. r. var. marifuga possess a maturing (not totally mature) gonad, a highly developed alimentary canal containing ingested food, and extensive haemopoietic tissue. Although the gills, thyroid gland, and the definitive kidneys are similar in both forms, incomplete regression of the larval kidney and the absence of a cranial pancreas in all L. r. var. marifuga imply that a slow sexual maturation is accompanied by a slow, and perhaps incomplete, metamorphosis. The incomplete metamorphosis is particularly exemplified in female L. r. var. marifuga and may account for the abnormal sex ratio of this variety. The retardation of sexual maturation in male L. r. var. marifuga permits the retention of a functional digestive system and, hence, provides an opportunity for feeding. The significance of these observations to present views on the evolution of lampreys is discussed.

Tagged juveniles from a strong year-class of sablefish (Anoplopoma fimbria) were sampled for 9 yr Tagged females were approximately 6 cm larger than untagged females at 50% maturity. Males showed little difference because of their slower growth rate. Untagged males and females matured one and 2 yr earlier than tagged males and females. From this same year-class length-at-age of untagged males and females was significantly larger than for tagged and recaptured fish. Untagged males and females were 6.5 and 8 cm larger than tagged fish by age seven. Smaller tagged fish were recaptured at lower rates than larger tagged fish, indicating that slower growth reduced recapture percentage, which we believe indicates a higher mortality rate. Because smaller size was associated with increased mortality and tagged fish grew slower than untagged fish, we concluded that tagged fish had higher rates of mortality than untagged fish. The increased age and size at 50% maturity and the increased juvenile mortality indicated the potential response of a population of sablefish and possibly other species to a reduction in individual fish growth. If our results apply to other species and other types of tags, investigators should be cautious in extrapolating from tagged to untagged populations.