Age-0 Juveniles Research Articles

First description and collection records of juvenile slime flounder Microstomus achne from the eastern and western coastal waters off Honshu Island, Japan

Morphological characteristics and body pigmentations of juvenile slime flounder Microstomus achne were described from one specimen [27.8 mm total length (TL)] collected off Niigata Prefecture from the Sea of Japan (35 m depth) in May 1993 and from three specimens (30.1, 36.2, and 40.9 mm TL) collected off Fukushima Prefecture on the Pacific coast of northern Japan (15 and 50 m depths) during April–May 2008 and 2009. These age-0 juveniles had a characteristically slenderly oval-shaped body and slightly protruded front nostrils. Sparsely distributed melanophores and xanthophores were clearly visible throughout the ocular side of one specimen, which was judged as a newly settled juvenile, whereas several spots aggregated by small melanophores were found in the others with elongated pectoral fins and small cycloid scales. Melanophores were only slightly detectable on the blind side. Comparisons of the depth distributions of slime flounder juveniles and sympatrically collected age-0 pleuronectids (Pseudopleuronectes herzensteini, Pseudopleuronectes yokohamae, Platichthys bicoloratus, and Dexistes rikuzenius) suggested that slime flounder can settle on broad nursery areas of coastal and offshore pleuronectid flatfishes, probably depending on local oceanic conditions during the protracted pelagic phase.

Are wild populations ideally distributed? Variations in density-dependent habitat use by age class in juvenile Atlantic salmon (Salmo salar)

We examined relationships between abundance and habitat use in three age classes of juvenile Atlantic salmon ( Salmo salar ) in the Stewiacke River, Nova Scotia, Canada. Using stream gradient as a proxy for habitat quality, we used a double half normal function, modified to include density dependence, to model the relationship between habitat quality and fish density. We found that density was asymmetrically distributed around a similar optimum gradient for all three age classes regardless of abundance. Habitat use was highly density-dependent for age-0 and age-1 juveniles, but not for age-2+ salmon. As abundance of age-0 and age-1 salmon increased, their relative density decreased in low-gradient habitat and increased in higher-gradient habitat, although their absolute density increased in all stream gradient categories. Variation in habitat use was consistent with ideal free theory for age-1 juveniles in high-gradient habitat, but not in low-gradient habitat. Age-2+ individuals appeared not to modify their distribution among habitats, even though increasing competition changes the relative benefit of low-gradient habitat in terms of resource acquisition. In contrast, age-1 individuals responded to increased competition by modifying their distribution along the habitat gradient, even though this may have slightly reduced an individual’s potential for growth.

Biological attributes of age-0 lake sturgeon in the lower Peshtigo River, Wisconsin

Lake sturgeon Acipenser fulvescens are imperiled throughout the Laurentian Great Lakes basin. Efforts to restore this species to former population levels have been ineffective due in part to limited information regarding its early life history. The objectives of this study were to characterize the larval drift and biological attributes of age-0 lake sturgeon in the lower Peshtigo River, Wisconsin. Lake sturgeon larvae were captured from May to June 2002 and 2003 using drift nets, while age-0 juveniles were captured from June through October 2002 and 2003 using wading, snorkeling, backpack electrofishing, and haul-seine surveys. Larval drift occurred within 14 days of adult spawning and extended from 1 to 3 weeks in duration, with two peaks in the number of fish drifting downstream each year. Larvae had a median total length (TL) of 19 mm (range: 13–23; N = 159) in 2002 and 18 mm (range: 13–24; N = 652) in 2003. Catch-per-unit-effort for larvae was 0.18 fish h−1 m2 and 0.94 fish h−1 m2 in 2002 and 2003, respectively. Age-0 juvenile lake sturgeon exhibited rapid growth (i.e. 2.57 mm day−1 in TL and 0.66 g day−1 in wet weight) throughout summer and fall months; relative condition of fish in both years was approximately 100, indicating good condition. Absolute abundance of age-0 juveniles in 2003 was estimated at 261 fish using the Schnabel estimator. The results from this study indicate that the lower Peshtigo River contains important nursery habitats suitable for age-0 lake sturgeon.

Population biology of carp (Cyprinus carpio L.) in the mid-Murray River and Barmah Forest Wetlands, Australia

The present study quantitatively describes a significant stock of carp (Cyprinus carpio L.), an exotic pest species, in a temperate riverine floodplain wetland. Intensity and duration of flooding influenced relative abundance, distribution and recruitment. Average growth (mm) in length was described with the von Bertalanffy growth model for males (L∞ = 489, k = 0.249, t0 = –0.519), and females (L∞ = 594, k = 0.177, t0 = –0.609) to age 28. Variation in growth was described with a lognormal distribution of k. Total mortality (Z year–1) was 0.268–0.407 for males, 0.311–0.422 for females, 3.24 for age-0 juveniles and 1.80 for age-1 juveniles. Natural mortality (M year–1) was 0.199 for males and 0.262 for females. Fishing mortality (F year–1) was <0.05 for males and 0.11–0.30 for females. Gonadal changes indicated extended spawning seasons peaking in September 1999 and October 2000. Median sizes and ages at initial maturation were 307 mm, 584 g and 1.1 years for males and 328 mm, 688 g and 2.7 years for females. Sex ratio varied significantly with age from equal as juveniles to a significant male-bias as adults. This description will enable better stock assessment and development of simulations that evaluate potential pest management strategies.

Residence Time and Seasonal Movements of Juvenile Coho Salmon in the Ecotone and Lower Estuary of Winchester Creek, South Slough, Oregon

Abstract The juvenile life history of coho salmon Oncorhynchus kisutch in the stream−estuary ecotone of Winchester Creek, South Slough, Oregon, was investigated in 1999–2001. Seines and a rotary screw trap were used to capture fish for dye-marking, and residence time within the ecotone was determined for recaptured marked fish. In the lower estuary, ultrasonic transmitters were used to document residence time and patterns of movement for smolts migrating to the ocean. Nearly half of each brood year moved to the estuary as subyearlings. A portion of age-0 juveniles that moved downstream during spring lived in the ecotone through summer for up to 8 months, then most moved back upstream to overwinter. Fish that moved to the ecotone during fall and winter had mean minimum residence times of 48 d in 1999 and 64 d in 2000. Some of the fish that moved to the ecotone during fall and winter moved into an off-channel beaver pond and resided there for a mean of 49 d. Spring age-1 smolts had a mean minimum residence ...

Effects of food consumption and temperature on growth rate and biochemical-based indicators of growth in early juvenile Atlantic cod Gadus morhua and haddock Melanogrammus aeglefinus

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 251:233-243 (2003) - doi:10.3354/meps251233 Effects of food consumption and temperature on growth rate and biochemical-based indicators of growth in early juvenile Atlantic cod Gadus morhua and haddock Melanogrammus aeglefinus Myron A. Peck1,5,*, Lawrence J. Buckley2, Elaine M. Caldarone3, David A. Bengtson4 1Graduate School of Oceanography, University of Rhode Island, South Ferry Road, Narragansett, Rhode Island 02882, USA 2URI/NOAA CMER Program, Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island 02882, USA 3National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Narragansett Laboratory, 28 Tarzwell Drive, Narragansett, Rhode Island 02882, USA 4Department of Fisheries, Animal, and Veterinary Science, University of Rhode Island, Kingston, Rhode Island 02881, USA 5Present address: Institute of Hydrobiology and Fisheries Research, University of Hamburg, Olbersweg 24, 22767 Hamburg, Germany *Email: myron.peck@uni-hamburg.de ABSTRACT: The relationship between the somatic growth rate (G) and feeding level (unfed, intermediate, and maximum rations) of age-0 juvenile cod Gadus morhua and haddock Melanogrammus aeglefinus was quantified at different temperatures. Laboratory trials were conducted using 2 size-classes of cod (3.6 to 5.6 cm standard length [SL], and 8.1 to 12.4 cm SL) at 5, 8, 12, and 15°C, and 1 size-class of haddock (6.0 to 9.6 cm SL) at 8 and 12°C. The shape of the growth-feeding relationship was well described by a 3-parameter asymptotic function for cod and by a linear function for haddock (R2 range = 0.837 to 0.966). The growth rate and scope for growth were maximum at 12°C, whereas growth efficiency was greatest (26.0 to 32.2%) at temperatures between 5 and 8°C. Juvenile cod held at 15°C exhibited reduced rates and efficiencies of somatic growth compared to fish at other temperatures. Biochemical-based growth indicators for age-0 juveniles were calibrated from measurements of the amounts of RNA, DNA, and protein in white muscle samples. A multiple linear regression using RNA:DNA and temperature as independent variables explained a significant portion of the variability observed in G of juvenile cod (R2 = 0.716) and haddock (R2 = 0.637). This relationship may be useful in estimating recent growth of age-0 juvenile cod and haddock in the field. KEY WORDS: Age-0 juvenile · Cod · Haddock · Feeding · Growth · RNA:DNA Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 251. Online publication date: April 11, 2003 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2003 Inter-Research.

Patterns in Abundance, Growth, and Mortality of Juvenile Red Drum across Estuaries on the Texas Coast with Implications for Recruitment and Stock Enhancement

Abstract The interannual variation in patterns of abundance, growth, and mortality of juvenile red drum Sciaenops ocellatus was examined with long-term monitoring data from nine estuaries along the Texas Gulf Coast during a 20-year period. Estimates of abundance and mortality exhibited order-of-magnitude differences. Growth rates varied two- to threefold across years within each estuary and across estuaries within a single year. For age-0 juveniles, abundance was typically highest in late fall, length increased exponentially, and mortality was generally low. Variation in growth and mortality was not related among estuaries, suggesting that the factors affecting the feeding and survival of young red drum are specific to individual estuarine systems. Estimates of age-0 red drum abundance were characterized by the intermittent occurrence of strong year-classes and were positively correlated across estuaries, indicating that factors determining abundance and distribution vary on a large spatial scale. Correla...

The Use of Microsatellite DNA Loci for Genetic Monitoring of Atlantic Salmon Populations

This work addresses the application of a new group of molecular markers, microsatellite loci, to monitor genetic diversity in stocks used in fish enhancement programs. To illustrate the potential use of these markers, we examined the genetic variation associated with the Connecticut River and Penobscot River populations of Atlantic salmon Salmo salar in the United States. Both rivers are stocked annually with fry from captive or cultured stocks that are one generation removed from sea-run adults. We analyzed microsatellite loci variation among sea-run adults and the derived cultured stock for the Connecticut River in a given year, along with two consecutive cohorts of cultured age-0 juveniles for the Penobscot River. Our results reveal subtle differences in allele frequencies between the two samples for each stock and some potential increases of homozygotes. These results demonstrate the potential value of microsatellite loci for routine genetic monitoring of cultured Atlantic salmon populations associated with restoration programs in the eastern United States.

Turbidity Reduces Predation on Migrating Juvenile Pacific Salmon

We field tested the hypothesis that predation by piscivorous fish is reduced in turbid compared with clear water. The Harrison River (⩽1 nephelometric turbidity units, NTU) is a clear tributary of the naturally turbid Fraser River (27–108 NTU), in British Columbia, Canada. Age-0 juveniles of Harrison River stocks of Pacific salmon Oncorhynchus spp. migrating seaward in spring obligately pass through turbid and clear reaches of these rivers. To test the hypothesis, we compared predation on salmonids by potential predators caught by beach seine and by the rate of predator attack on tethered juvenile chinook salmon O. tshawytscha in these two rivers. Of 491 predators examined, 30% of Harrison River piscivores had recently consumed fish compared with only 10% of Fraser River piscivores. Of those that ate fish, fish prey per predator was significantly lower in the Fraser River (mean = 1.1, N = 21) than in the Harrison River (mean = 1.7, N = 66). In a clear-water side channel of the Fraser River—Nicomen Slough (1–6 NTU)—both incidence of predation (37%) and number of fish prey per predator (mean = 2.4, N = 19) were similar to values for the Harrison River. Loss of prey from tethers was significantly higher in the Harrison River (23–61%) than in the Fraser River (10–24%). The loss of prey from tethers was highest at dusk and near the bottom in the Harrison River; no spatial or temporal difference occurred in the turbid Fraser River. Therefore, our data support the hypothesis. During their seaward migration in the Fraser River system, age-0 Pacific salmon were less likely to encounter and be consumed by fish piscivores in turbid water than in clear water.

Prey selection by age-0 walleye pollock, Theragra chalcogramma, in nearshore waters of the Gulf of Alaska

Juvenile walleye pollock, Theragra chalcogramma, is the dominant forage fish on the continental shelf of the Gulf of Alaska, yet little is known about the feeding habits of this important interval of pollock life history. The taxonomic composition and size of prey found in the stomachs of age-0 juveniles collected at three nearshore locations in the Gulf of Alaska in September 1990 were compared to the composition and size of zooplankton collected in concurrent plankton tows. The maximum length of prey consumed increased dramatically over the length range of pollock examined (58–110 mm) from approximately 7 mm to 30 mm, due mainly to the consumption of large euphausiids and chaetognaths by the bigger individuals. The maximum width of prey changed little over this size range although there was a general increase in prey width with increasing predator size. The minimum prey length and width did not change with increasing fish size. Juvenile pollock generally selected the larger prey sizes relative to what was available. Juvenile pollock showed a marked preference for adult euphausiids and decapod larvae and an avoidance of copepods and chaetognaths relative to the numbers collected in net tows. These results are discussed relative to the feeding ecology of these juvenile fishes.

Abundance and Assemblage Structure of Fish Larvae in the Lower Missouri River and Its Tributaries

Most of the backwater habitat in the floodplain of the lower Missouri River has been eliminated, but the lower reaches of tributaries have flow and depth characteristics similar to backwaters. We sampled the assemblages of fish larvae and age-0 juveniles in the lower 8 km of four tributaries and in the Missouri River main channel to determine the extent to which riverine species use these backwaters for early life history stages. We also sought to determine which tributary characteristics were associated with use by riverine species. Densities of 8 of the 10 fish taxa analyzed were greater in tributaries than in the Missouri River in 1987 and 1988. The composition of the larval fish fauna varied: carpsuckers Carpiodes spp., goldeye Hiodon alosoides, freshwater drum Aplodinotus grunniens, and common carp Cyprinus carpio occurred in large rivers; whereas mostly gizzard shad Dorsosoma cepedianum, nearctic cyprinids (mostly emerald shiner Notropis atherinoides and red shiner Cyprinella lutrensis), and sunfishes Lepomis spp. occurred in small tributaries. Assemblages in large tributaries included large-river and small-tributary taxa. The gradient in assemblage composition, from small-tributary fauna to large-river fauna, corresponded to a gradient in channel morphometry, from shallow waters and coarse substrate to greater channel depths and fine sediments. The complex pattern of flow between the Missouri River and its tributaries and the diversity of tributary morphometry were associated with, and may be critical to, productivity and the maintenance of a diverse fish fauna.

Seismic refraction studies off the coast of Alaska: 1956–1957 : Shor G. G., Jr. 1962. Bull. Seismol. Soc. 52 (1): 37–57

We investigated the connectivity of walleye pollock in the Gulf of Alaska (GOA) and linkages to the Bering Sea (BS) and Aleutian Island (AL) regions. We used a spatially-explicit Individual-based model (IBM) coupled to 6 years of a hydrodynamic model that simulates the early life history of walleye pollock in the GOA (eggs to age-0 juveniles). The processes modeled included growth, movement, mortality, feeding and the bioenergetics component for larvae and juveniles. Simulations were set to release particles on the 1st of the month (February to May) in fourteen historical spawning areas in the GOA up to the 1st of September each year. Model results reproduced the link between the Shelikof Strait spawning area and the Shumagin nursery region for March and April spawners, besides other Potential Nursery Areas (PNAs) found in the GOA. A prominent finding of this study was the appearance of the BS as important PNAs for several GOA spawning grounds, which is supported by a consistent flow into the BS through Unimak Pass. The simulations showed the highest density of simulated surviving pollock in the western Bering Sea (WBS) region with the lowest coefficients of variation of the whole domain. Three spawning sectors were defined, which aggregate multiple spawning areas in the eastern (EGOA), central (CGOA) and western Gulf of Alaska (WGOA). A connectivity matrix showed strong retention within the CGOA (25.9%) and EGOA (23.8%), but not in the WGOA (7.2%). Within the GOA, the highest connectivity is observed from EGOA to CGOA (57.8%) followed by the connection from CGOA to WGOA (24.3%). Overall, one of the most prominent connections was from WGOA to WBS (62.8%), followed by a connection from CGOA to WBS (29.2%). In addition, scenarios of shifting spawning locations and nursery sectors of GOA, BS and AL are explored and implications for walleye pollock stock structure hypotheses are discussed.