Freshwater Growth Research Articles

Influences of Freshwater and Marine Growth on the Egg Size–Egg Number Tradeoff in Coho and Chinook Salmon

How to partition a finite amount of energy into progeny is an important issue in evolutionary biology. Salmonids produce a small number of large eggs compared with other teleost fishes, and there are positive correlations between female size and both the size and number of eggs produced. We examined the temporal variation in reproductive investment (gonad mass, fecundity, and egg size) of coho salmon Oncorhynchus kisutch and Chinook salmon O. tshawytscha at the University of Washington hatchery over the last three to five decades. During this period, fish growth rates in freshwater and at sea varied greatly, allowing us to test the hypotheses that rapid early growth rate results in high fecundity and that hatchery populations evolve high fecundity over time. In the coho salmon, reductions in length, condition factor, and size-adjusted fecundity over the past decades combined to reduce overall average fecundity to only about half its former level. In Chinook salmon, age at maturity decreased as smolt size increased, so average size decreased over time but size at a given age did not decline. Reproductive investment (gonad size, corrected for body size) decreased for the coho salmon but not for the Chinook salmon. Egg size (adjusted for variation in fish size) did not vary with growth rate for either species or environment. Size-adjusted fecundity did not increase with increasing freshwater growth for either species, but it did increase with marine growth for the coho and age-3 Chinook salmon. These results contradict the prediction that females adjust egg size depending on the perceived quality of the juvenile habitat. Egg size is probably determined much later in life, corresponding to the number of remaining eggs and the energetic constraints at maturity. The results are also inconsistent with the hypothesis that hatchery populations will evolve small eggs and high fecundity as a result of a relaxed selection for large fry.

Multi-year effects of high densities of sockeye salmon spawners on juvenile salmon growth and survival: a case study from the Exxon Valdez oil spill

Reduced fishing after the 1989 Exxon Valdez oil spill in Prince William Sound, Alaska, contributed to exceptionally large numbers of sockeye salmon spawners up to 860 km from the spill site. We measured annual scale growth of adult sockeye salmon from four affected populations, 1970–1997, in order to test the hypothesis that large spawner densities can have multi-year effects on juvenile size and subsequent adult abundances as a result of intraspecific competition among juveniles in the nursery lake. Sockeye salmon scale growth in fresh water was significantly reduced by the large 1989 spawner densities in the Kenai River system, Red Lake, Akalura Lake, but not Chignik Lake. Scale growth in the three affected systems recovered to previous levels 2–4 years after the oil spill, but subsequent moderately high spawner densities led to exceptionally low growth. Juvenile salmon growth was negatively related to parent spawners, spawners from the next brood year (second season in lake), and spawners from the previous brood year. Multi-variate time series analyses indicated adult sockeye salmon abundance increased with greater numbers of parent spawners, but decreased as a result of either large numbers of spawners in the previous year or small juvenile salmon size. These results indicate sockeye salmon spawners can affect juvenile growth and adult production of adjacent year classes. Implications for stock-recruitment modeling and spawner density management are discussed.

Growth hormone and insulin-like growth factor I of a Euryhaline fish Cottus kazika: cDNA cloning and expression after seawater acclimation

The four-spine sculpin Cottus kazika is a euryhaline teleost, in which faster growth in seawater (SW) and freshwater (FW) has been reported. In this study, cDNA clones encoding growth hormone (GH) and insulin-like growth factor I (IGF-I) were isolated from this species to examine the involvement of the GH/IGF-I axis in osmotic adaptation. The amino acid sequence of GH predicted from cDNA was highly similar to those of other fish species, 92% to Sparus aurata, 67% to Paralichthys olivaceus, and 63% to Oncorhynchus keta. The predicted sequence of IGF-I was also exhibited high similarity to those of other fishes, 97% to Myxocephalus scorpius, 95% to P. olivaceus, and 81% to O. keta. Tissue distribution of GH and IGF-I mRNA in fish reared in FW and SW was examined by reverse transcription-polymerase chain reaction (RT-PCR). The GH mRNA was detected only in the pituitary gland. The major site of IGF-I mRNA expression was the liver while minor signals were detected in various tissues including the pituitary, gill, fin, heart, spleen, intestine, and kidney. The expression level of GH mRNA in the pituitary was not different between FW- and SW-reared fish. However, the level of IGF-I mRNA in the liver of SW-reared fish was significantly higher than that of FW-reared fish. These results suggest the possible involvement of hepatic IGF-I in SW adaptation of this species.

Migration, speciation, and the evolution of diadromy in anguillid eels

Recent findings and hypotheses about the migration, spawning ecology, phylogenetic relationships, and possible mechanisms of speciation of anguillid eels are overviewed. The offshore distribution and otolith microstructure of small leptocephali suggest that the Japanese eel Anguilla japonica may spawn at seamounts west of the Mariana Islands in the western North Pacific during the new moon of each month from April to November. Some temperate eels have been found to remain in coastal areas after recruitment without a freshwater growth phase (ocean residents or "sea eels"), showing flexible patterns of migratory histories. Recent molecular phylogenetic studies suggest that the tropical eel Anguilla borneensis from the Borneo Island region is the most ancestral species. Every eel species or population has its own migration loop (migration route or life cycle) that connects their spawning area and growth habitats. Spatial and temporal shifts in these migration loops could cause separation into subpopulations, or speciation. Therefore, the large-scale migration of temperate eels probably evolved from local migrations of tropical eels as a result of long-distance dispersal of leptocephali from spawning sites in tropical waters of low latitude to temperate growth habitats at higher latitudes.

Identification of Steelhead and Resident Rainbow Trout Progeny in the Deschutes River, Oregon, Revealed with Otolith Microchemistry

Abstract Comparisons of strontium:calcium (Sr: Ca) ratios in otolith primordia and freshwater growth regions were used to identify the progeny of steelhead Oncorhynchus mykiss (anadromous rainbow trout) and resident rainbow trout in the Deschutes River, Oregon. We cultured progeny of known adult steelhead and resident rainbow trout to confirm the relationship between Sr:Ca ratios in otolith primordia and the life history of the maternal parent. The mean (±SD) Sr:Ca ratio was significantly higher in the otolith primordia of the progeny of steelhead (0.001461 ± 0.00029; n = 100) than in those of the progeny of resident rainbow trout (0.000829 ± 0.000012; n = 100). We used comparisons of Sr:Ca ratios in the primordia and first-summer growth regions of otoliths to determine the maternal origin of unknown O. mykiss juveniles (n = 272) collected from rearing habitats within the main-stem Deschutes River and tributary rearing habitats and thus to ascertain the relative proportion of each life history morph in ea...

Salinity effects on osmoregulation and growth of the euryhaline flounder Paralichthys orbignyanus

The flounder, Paralichthys orbignyanus, is found in coastal and estuarine waters of the Western South Atlantic Ocean. It is being considered for aquaculture due to its high market price and wide tolerance to environmental factors such as salinity, pH, and nitrogenous compounds. The objective of this study was to characterize the ionic and osmotic regulation of P. orbignyanus over the range of its tolerated ambient salinities (0–40‰) and to evaluate the survival and growth in freshwater (0‰) and seawater (30‰) over 90 days. After 15 days of exposure to different salinities (0‰, 10‰, 20‰, 30‰ and 40‰), plasma osmolality and ionic (Na +, Cl −, K + and Ca 2+) concentrations slightly increased with salinity. The isosmotic point was estimated as 328.6 mOsm kg −1 H 2O and corresponded to 10.9‰ salinity. After 90 days, survival was similar in freshwater and seawater, but osmo- and ionoregulation was significantly affected in freshwater and flounders reared in this medium showed a lower growth rate than those reared in seawater. Based on the results from this study, P. orbignyanus can be characterized as a marine/estuarine euryhaline teleost capable of hyper/hypo iono- and osmoregulation over the fluctuating salinity regime faced by this species in the environment. Furthermore, results suggest that the lower growth rate exhibited by P. orbignyanus in freshwater could be due, at least partially, to a higher energy expenditure associated to a higher branchial Na +, K +-ATPase activity in this environment.

Modelling of Spirulina platensis growth in fresh water using response surface methodology

The influence of nutrient addition on the growth rate of Spirulina platensis in the Mangueira Lagoon water was studied in order to investigate the feasibility of using this water for biomass production. The addition of urea and sodium bicarbonate was studied through surface response methodology, over concentration ranges from 0.0 to 0.01170 M, and 0.0–19.70 gl−1 respectively. The growth of Spirulina platensis in Mangueira Lagoon water with no addition of nutrients was carried out and compared with the biomass growth after nutrient addition. The results indicated that the optimal level of nutrients was 0.00585 M urea and without the addition of sodium bicarbonate. The biomass concentration was 1.4 gl−1 in 780 h of cultivation and the doubling time (t d) was 3.85 days. In 300 h, the biomass concentration in the medium without nutrient addition was 0.9 gl−1, with a doubling time of 3.80 days.

The Demise of Owikeno Lake Sockeye Salmon

A persistent period of low abundance in what was once the second largest fishery for sockeye salmon Oncorhynchus nerka in British Columbia has kept the Rivers Inlet fishery closed since 1996. Initial speculation about the cause of the decline focused on factors such as reduced egg-to-fry survival, declining quantity and quality of spawning habitat, and reduced fry-to-smolt survival in Owikeno Lake (the only nursery lake in Rivers Inlet). We developed an index of juvenile sockeye salmon abundance by combining direct estimates of abundance from trawl surveys with indirect estimates of abundance inferred from density-dependent growth of juvenile sockeye salmon. Juvenile growth data were available as either direct samples of presmolt weight or as measurements of freshwater growth from the scales of returning adults. Collectively, these data do not indicate a long-term decline in juvenile sockeye salmon abundance since the 1950s. Throughout the 1970s and 1980s and even more recently (1991 and 1994 brood years), the juvenile abundance index exceeded the long-term mean. If freshwater abundance was either untrended or increasing, the most likely cause of the population decline would have been lower survival after the fry stage, which would have been noticeable in the 1970s and especially from 1992 to 1998. Poor marine survival is the most parsimonious explanation for the declining fry-to-adult survival in Owikeno Lake, particularly in light of coincident declines in sockeye salmon returns per spawner at Long Lake (a nearby pristine watershed) and declines in adult sockeye salmon abundance in other populations to the north of Rivers Inlet.

Effects of temperature, irradiance and photoperiod on growth and pigment content in some freshwater red algae in culture

SUMMARY The responses of relative growth rate (% day‐1) and pigment content (chlorophyll a, phycocyanin and phycoerythrin) to temperature, irradiance and photoperiod were analyzed in culture in seven freshwater red algae: Audouinella hermannii (Roth) Duby, Audouinella pygmaea (Kutzing) Weber-van Bosse, Batrachospermum ambiguum Montagne, Batrachospermum delicatulum (Skuja) Necchi et Entwisle, ‘Chantransia’ stages of B. delicatulum and Batrachospermum macrosporum Montagne and Compsopogon coeruleus (C. Agardh) Montagne. Experimental conditions included temperatures of 10, 15, 20 and 25°C and low and high irradiances (65 and 300 µmol photons m‐2 s‐1, respectively). Long and short day lengths (16:8 and 8:16 LD cycles) were also applied at the two irradiances. Growth effects of temperature and irradiance were evident in most algae tested, and there were significant interactions among treatments. Most freshwater red algae had the best growth under low irradiance, confirming the preference of freshwater red algae for low light regimens. In general there was highest growth rate in long days and low irradiance. Growth optima in relation to temperature were species-specific and also varied between low and high irradiances for the same alga. The most significant differences in pigment content were related to temperature, whereas few significant differences could be attributed to variation in irradiance and photoperiod or interactions among the three parameters. The responses were species-specific and also differed for pigments in distinct temperatures, irradiances and photoperiods in the same alga. Phycocyanin was generally more concentrated than phycoerythrin and phycobiliproteins were more concentrated than chlorophyll a. The highest total pigment contents were found in two species typical of shaded habitats: A. hermannii and C. coeruleus. The expected inverse relationship of pigment with irradiance was observed only in C. coeruleus. In general, the most favorable conditions for growth were not coincident with those with highest pigment contents.

Salt tolerance in Phragmites australis populations from coastal Mediterranean marshes

Responses to salt in soil interstitial water were studied experimentally for nine populations of Phragmites australis (Cav.) Trin. ex Steud. from coastal Mediterranean marshes in France. The effects of exposure to salinity ranging from 0 to 25‰ were measured on germination of seeds collected in each site. Germination was up to 100% and was affected by salinity above 10‰. Variation in germination among populations was small in freshwater (ranging from 89 to 99% on average) but saline conditions increased the contrast (5–60% at 25‰). Growth of seedlings in shoot and biomass production were measured during a 2-month exposure to constant saline solutions, ranging from 0 to 20‰. The effects on the number and length of shoots from a 25-day temporary exposure at 25‰ followed by recovery in freshwater were measured. Growth decreased with increasing salinity (50% decrease at 7.5‰ when compared to freshwater) and 7–100% mortality depending on population, occurred at 15 and 20‰. Cumulative shoot length and biomass production varied significantly among populations in freshwater, but the difference was small in saline conditions, significant for biomass but not for length. The 25-day exposure at 25‰ stopped growth and plants recovered after flushing with freshwater. The stress effect was significant for shoot length but not for shoot number. Twenty-five days after the treatment ended, the numbers of shoots were not different between exposed seedlings and controls. The temporary stress suppressed the differences among populations but they were restored during subsequent growth in freshwater. None of the variation patterns observed during the experiment were related to the present condition of the site of origin.

Photoperiod control and influence of body size on off-season parr–smolt transformation and post-smolt growth

To examine the combined effects of photoperiod and body size on off-season parr–smolt transformation and post-smolt growth, groups of small and large graded potential Atlantic salmon smolts (initial size 10 and 23 g) were raised under four different photoperiods between 26 July and 14 November. Photoperiod treatments included a 10 months phase-advance of simulated natural photoperiod (SNPa, from LD12:12 to LD24:0 over 16 weeks); two square wave photoperiod regimes; which were continuously light interrupted by LD12:12 for 9 (9) or 12 (12) weeks, respectively; and continuous light (LD24:0). Photoperiod manipulation significantly influenced growth and hypo-osmoregulatory ability. Between July and November, smolts raised on SNPa and LD12:12 (9) showed an increase in seawater tolerance, concurrent with an increase in Na +, K +-ATPase activity and a decrease in condition factor (CF). No differences in plasma chloride levels were seen among the small and large graded smolts (SG and LG), whereas a higher Na +, K +-ATPase activity was recorded in the small smolts at weeks 12, 14, and 16. Higher growth rates were seen in the small smolts during the freshwater period. Continuous light increased growth in freshwater, but interfered with smolt development. Following transfer to seawater, both SG and LG previously held under SNPa and LD12:12 (9) grew better than the fish reared under LD24:0, which showed a decrease in growth. The high growth rates in seawater in the SNPa and LD12:12 (9) groups concur with the good smolt status prior to transfer. Our findings indicate that both SNPa and LD12:12 (9) can be recommended in the production of off-season salmon smolts and among the smolt parameters monitored, gill Na +, K +-ATPase activity appears to be the most reliable indicator of smolt status.

Population structure of sympatric anadromous and nonanadromousOncorhynchus mykiss: evidence from spawning surveys and otolith microchemistry

Reproductive isolation between steelhead and resident rainbow trout (Oncorhynchus mykiss) was examined in the Deschutes River, Oregon, through surveys of spawning timing and location. Otolith microchemistry was used to determine the occurrence of steelhead and resident rainbow trout progeny in the adult populations of steelhead and resident rainbow trout in the Deschutes River and in the Babine River, British Columbia. In the 3 years studied, steelhead spawning occurred from mid March through May and resident rainbow trout spawning occurred from mid March through August. The timing of 50% spawning was 9-10 weeks earlier for steelhead than for resident rainbow trout. Spawning sites selected by steelhead were in deeper water and had larger substrate than those selected by resident rainbow trout. Maternal origin was identified by comparing Sr/Ca ratios in the primordia and freshwater growth regions of the otolith with a wavelength-dispersive electron microprobe. In the Deschutes River, only steelhead of steelhead maternal origin and resident rainbow trout of resident rainbow trout origin were observed. In the Babine River, steelhead of resident rainbow trout origin and resident rainbow trout of steelhead maternal origin were also observed. Based on these findings, we suggest that steelhead and resident rainbow trout in the Deschutes River may constitute reproductively isolated populations.

Isolation of bacteriophages specific to a fish pathogen, Pseudomonas plecoglossicida, as a candidate for disease control.

Two types of bacteriophage specific to Pseudomonas plecoglossicida, the causative agent of bacterial hemorrhagic ascites disease in cultured ayu fish (Plecoglossus altivelis), were isolated from diseased ayu and the rearing pond water. One type of phage, which formed small plaques, was tentatively classified as a member of the family Myoviridae, and the other type, which formed large plaques, was classified as a member of the family Podoviridae. All 27 strains of P. plecoglossicida examined, which were isolated from diseased ayu from geographically different areas in 1991 to 1999, exhibited quite similar sensitivities to either type of phage. One strain of P. plecoglossicida was highly virulent for ayu, and the 50% lethal dose (LD(50)) when intramuscular injection was used was 10(1.2) CFU fish(-1); in contrast, phage-resistant variants of this organism were less virulent (LD(50), >10(4) CFU fish(-1)). Oral administration of phage-impregnated feed to ayu resulted in protection against experimental infection with P. plecoglossicida. After oral administration of P. plecoglossicida cells of this bacterium were always detected in the kidneys of control fish that did not receive the phage treatment, while the cells quickly disappeared from the phage-treated fish. Bacterial growth in freshwater was lower in the presence of phage, and the number of phage PFU increased rapidly. These results suggest that it may be possible to use phage to control the disease caused by P. plecoglossicida.

Population structure of sympatric anadromous and nonanadromous <i>Oncorhynchus mykiss</i>: evidence from spawning surveys and otolith microchemistry

Reproductive isolation between steelhead and resident rainbow trout (Oncorhynchus mykiss) was examined in the Deschutes River, Oregon, through surveys of spawning timing and location. Otolith microchemistry was used to de- termine the occurrence of steelhead and resident rainbow trout progeny in the adult populations of steelhead and resi - dent rainbow trout in the Deschutes River and in the Babine River, British Columbia. In the 3 years studied, steelhead spawning occurred from mid March through May and resident rainbow trout spawning occurred from mid March through August. The timing of 50% spawning was 9-10 weeks earlier for steelhead than for resident rainbow trout. Spawning sites selected by steelhead were in deeper water and had larger substrate than those selected by resident rain - bow trout. Maternal origin was identified by comparing Sr/Ca ratios in the primordia and freshwater growth regions of the otolith with a wavelength-dispersive electron microprobe. In the Deschutes River, only steelhead of steelhead mater - nal origin and resident rainbow trout of resident rainbow trout origin were observed. In the Babine River, steelhead of resident rainbow trout origin and resident rainbow trout of steelhead maternal origin were also observed. Based on these findings, we suggest that steelhead and resident rainbow trout in the Deschutes River may constitute reproduc- tively isolated populations.

A Mathematical Equation for Describing Growth of Freshwater Species

ABSTRACT We introduced a new four-parameter growth equation and tested it with observed growth data sets for a variety of aquatic species. The equation is: W = W f ,—(W f —W 0)/{c· (1—W 0/W f ) · [1—exp(kt)] + exp(kt)} where W f , and W 0, are the upper asymptotic and initial values respectively, and c and k are constants. The new equation is a modification of the logistic and the Spillman equations with a special value of parameter c. Unlike the logistic and the Spillman functions, the new model has an unfixed value of the inflection point as dictated by the additional parameter c. We compared the model to the logistic, Spillman, Gompertz, and Bertalanffy equations using 10 sets of reference growth data of freshwater species ranging from protozoans to crustaceans to fishes. The new equation yielded excellent fits to each data set, which suggests that it is worthy of being considered by freshwater growth data analysts.

Ambient salinity modulates the response of the tilapia, Oreochromis mossambicus (Peters), to net confinement

The stress response of the euryhaline tilapia Oreochromis mossambicus adapted to either fresh water (FW) or salt water (Instant Ocean™, 950 mosm; (SW)) was investigated to establish the influences of ambient salinity in this species. The fish were considered to be adapted to the salinities as pre-confinement plasma cortisol and glucose levels were typical for unstressed fish. Two hour net confinement increased plasma cortisol and glucose to a similar extent in both FW and SW. Individual plasma sodium and chloride levels were unaffected by confinement, although plasma Na:Cl ratio increased in FW. Confinement increased intestinal Na +/K +-ATPase activity in FW, but not in SW. In contrast, kidney Na +/K +-ATPase activity increased in SW only. Branchial Na +/K +-ATPase activity decreased with confinement in SW, but not in FW. In SW, confinement reduced the numbers of opercular chloride cells. Increased aging of the branchial chloride cell (CC) population of SW-confined fish was indicated by large numbers of apoptotic CCs in the interlamellar areas. This effect on the CC population was absent in FW-confined fish. Overall, confinement in SW-adapted fish had a more profound impact than confinement in FW-adapted fish. This is likely to have associated energetic consequences in terms of branchial oxygen and ATP consumption. Therefore, results suggest the possibility of different effects of confinement on subsequent growth in FW and SW.

Exposures to low-level ionizing radiation: Effects on biochemical and whole-body indices of growth in juvenile brook charr (Salvelinus fontinalis)

Exposure to ionizing radiation (IR) was used to alter gonadal growth in brook charr (Salvelinus fontinalis). To evaluate the possible effects of low-level doses of IR on future seawater adaptability of brook charr, the physiological state and growth performances of juvenile brook charr were examined for 15 months. Four groups of fish were exposed to different experimental doses of IR at the hatching stage: 0 (control), 6.2, 7.8, and 11.4 Gy. Growth in length and weight and condition factors of the irradiated groups were initially impaired compared with the control. Differences in growth were observed and were proportional to the irradiation dose. Initial growth delay in the irradiated groups was followed by compensatory growth of sufficient magnitude and duration that similar weights and lengths among all groups were reached by the end of the growth trial. Changes in the concentration of nucleic acids, protein, and water content were evaluated at three trimestrial intervals in the control and 11.4 Gy groups. DNA content was systematically found to be higher in the irradiated groups compared with the control (602.76 and 850.38 μg/g wet tissue). No difference in protein content (mg/g) in relation to fish weight was found between both groups during the freshwater growth period. Lipid analysis was performed on the final samples and was found to be significantly higher in the irradiated groups displaying catch-up growth (8.2% and 11.4% wet weight). RNA/DNA, RNA/protein, and protein/DNA were also calculated. J. Exp. Zool. 283:315–325, 1999. © 1999 Wiley-Liss, Inc.

Effects of long‐term exercise on survival, homing and straying of released Atlantic salmon smolts

Atlantic salmon 1+ pre‐smolts were exercised under low (LE) or moderate (ME) water current velocities prior to release. The flow regimes had a minor effect on freshwater growth and did not affect total Carlin‐tag recaptures significantly, but the LE adults strayed more frequently and the ME salmon homed more successfully to the release site.

Comparisons of cultured triploid and diploid Atlantic salmon (Salmo salar L.)

The use of sterile, triploid salmon for aquaculture would be an effective method of preventing genetic interactions between cultured and wild salmon. The studies presented in this paper compare the performance of six year classes of triploid and diploid salmon in freshwater and seawater stages of commercial production. Freshwater growth was comparable between triploids and diploids. Freshwater survival was also similar between triploids and diploids except that survival was lower in the triploids for the developmental interval between fertilization and first feeding. In sea water, triploids performed better than diploids in terms of growth. However, survival was lower in triploids and they showed a higher incidence of jaw deformities. In summary, the overall yields of triploids was lower than diploids under culture conditions.

Form changes in the sea bass, Dicentrarchus labrax (Moronidae: Teleostei), after acclimation to freshwater: an analysis using shape coordinates

Morphological changes in the sea bass, Dicentrarchus labrax (Perciformes: Moronidae), were investigated after an experimental acclimation trial to freshwater. The sea bass is an euryhaline species occurring in the Mediterranean and west Atlantic from 30° N to 55° N. Part of the offspring of a pool of breeders was acclimated to freshwater at 9 months of age while maintaining the original stock in marine water. The effect of acclimation to freshwater over the entire form of the fish was studied through geometric morphometrics (shape coordinates). Changes in the form were shown graphically as landmark displacements though age classes 7,12, 15, 19 and 24 months and were discussed in the light of integrated growth. A significantly faster growth in freshwater was detected. Shape coordinates analyzed through multivariate statistics show that significant differences in shape arise after acclimation to freshwater. Moreover, the uniform component of shape change reveals a major effect of stretching or compression perpendicular to the body axis which is common and conservative in both trials. Differences are discussed in terms of selection and ecophenotypism.