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Migrations of springtime Alewife Alosa pseudoharengus and Blueback Herring A. aestivalis, collectively referred to as river herring, are monitored in many rivers along the Atlantic coast to estimate population sizes. While these estimates give an indication of annual differences in the number of returning adults, links to the subsequent timing and duration of spawning and freshwater juvenile productivity remain equivocal. In this study, we captured juvenile river herring at night in 20 coastal Massachusetts lakes using a purse seine and extracted otoliths to derive daily fish ages and back-calculate spawn dates. Estimates of spawning dates were compared with fishway counts of migrating adults to assess differences in migration timing and the timing and duration of spawning. We observed a distinct delay between the beginning of the adult migration run and the start of spawning, ranging from 7 to 28 d across the 20 lakes. Spawning continued 13–48 d after adults stopped migrating into freshwater, fur...

Recent declines in anadromous river herring (Alewife Alosa pseudoharengus and Blueback Herring A. aestivalis) have been documented in much of their range using fishery-independent spawning run counts. A lack of rigorous long-term run counts and demographic data for Chesapeake Bay spawning stocks resulted in the declaration of unknown stock status in a 2012 stock assessment and made it difficult to evaluate responses to conservation and restoration efforts. The objectives of the present study were to (1) conduct the first spawning run counts of river herring in the Choptank River, Maryland, since the run counts performed over a 2-year period in 1972 and 1973, (2) evaluate population structure and dynamics, and (3) identify environmental variables associated with run timing. Spawning runs of Alewives and Blueback Herring were recorded from March 10 to June 4, 2014, using imaging sonar and processed manually to produce hourly run counts of fish with TLs ranging from 200 to 350 mm. A total of 1,659,09...

The purpose of this study was to document timing and habitat of alosines (Hickory Shad Alosa mediocris, American Shad A. sapidissima, Alewife A. pseudoharengus, and Blueback Herring A. aestivalis) and Striped Bass Morone saxatilis in the lower Tar River, a North Carolina coastal watershed partially restricted by an unused industrial dam. Alosines and Striped Bass are usually separated in time or space during spawning activity but occasionally overlap in some systems. Results show that both eggs and larvae of Hickory Shad and Striped Bass predominated catches, followed by American Shad. Alewife and Blueback Herring had negligible catches of eggs and larvae, but a separate study conducted 48 river kilometers downstream of the study area collected larvae of both species. Eggs and larvae of target species overlapped spatially and were most abundant in downstream tributaries, which seasonally reached hypoxic to anoxic conditions. The origins of spawning are unknown, but the collection of eggs suggests ...

Manganese is a commonly found constituent in fish otoliths, yet a direct correlation with ambient water concentrations as observed for other elements has proven elusive. There is compelling evidence that Mn uptake is related to the availability of reduced Mn (Mn2+) resulting from hypoxia (Limburg et al. 2015) but that fish growth rate also plays a role. We tested the latter possibility by examining otoliths from anadromous river herring (Alewife Alosa pseudoharengus and Blueback Herring A. aestivalis) in New York waters. A significant correlation was found between the ages at which shifts in otolith daily growth increments (assumed proportional to somatic growth) and shifts in otolith Mn:Ca ratios were detected. Furthermore, significant positive Spearman's rank correlations were observed between mean otolith daily growth and otolith Mn:Ca. Species- and site-specific differences were evident, but significant positive correlations were found for these relationships within each species and at most sa...

River herring (Alewives Alosa pseudoharengus and Blueback Herring A. aestivalis [bluebacks]) are congeneric, anadromous clupeid fishes that hybridize in areas of sympatry. Peritoneal pigmentation is the most diagnostic characteristic used to distinguish the species, but pigmentation has not been examined in hybrids. We developed a molecular-based assay to distinguish purebred river herring species from F1 hybrids and compared the peritoneal pigmentation among captive-raised purebred and hybrid individuals. Both wild-caught Alewife and blueback females tank-spawned with conspecific and congeneric males, but Alewives required exogenous hormone administration. Larvae of both species and hybrids were raised for ∼290 d posthatch, and peritoneal pigmentation was quantified. A nuclear gene (rag2) restriction fragment length polymorphism assay was used for species and hybrid identification. The peritoneal pigmentation was significantly darker in hatchery-spawned bluebacks than in Alewives, and hybrids exh...

We investigated the spatial and temporal accuracy of otolith chemistry for distinguishing populations (and subpopulations) of anadromous river herring (Alewife Alosa pseudoharengus and Blueback Herring A. aestivalis) from New York watersheds. Water chemistry of selected analytes (Sr:Ca, Ba:Ca, 87:86Sr, and δ18O) differed spatially and interannually among sites within the Hudson River as well as between the Hudson River and Long Island estuaries. Otolith chemical markers for juvenile river herring differed significantly among all sampling sites, with combined elemental and isotopic ratios differing significantly between species and between years, although the effect of year did not influence assignments at broad spatial scales (i.e., 105 m). Adult river herring collected in the Hudson River were assigned to natal sites using all juvenile otolith markers except δ18O, which had methodological problems. Adult Alewives and Blueback Herring were classified to Hudson River populations at 73% and 42%, res...

Blueback herring Alosa aestivalis are anadromous, iteroparous, winter spawners in the St. Johns River, Florida, but published data about this population are limited. We collected adults by electrofishing in the upper St. Johns River during the 2002–2005 spawning runs to examine the abundance, distribution, size, sex ratio, reproductive biology, and feeding habits of the population. When possible, data from the present study were compared with those for blueback herring collected with seine nets in the lower St. Johns River during the 1972 and 1973 spawning runs. Blueback herring began upstream migration by January and stayed in the river until at least April. The average fish size was significantly smaller in 2002–2005 than in 1972–1973, but sex ratios were not different from 1:1 in 5 of the 6 years studied. The more recent collections suggest that blueback herring females released multiple batches of eggs during one spawning season (spawning a batch every 3–4 d on average) and that spawning occu...

This study addressed the question whether the increase in the abundance of striped bass Morone saxatilis in the Hudson River that began after 1990 and the associated increase in predatory demand could have been responsible for the observed declines in the abundance of juvenile river herring (i.e., blueback herring Alosa aestivalis and alewife A. pseudoharengus), Atlantic tomcod Microgadus tomcod, and white perch Morone americana as well as the apparent decline in the survival of juvenile striped bass in the Hudson River. The seasonal (August through October) predatory demand of Hudson River striped bass (ages 1-13) was estimated to have increased from an average of 3.4 million kg/year for the period 1982-1990 to an average of 15.0 million kg/year for the period 1991-2004. Since 1990, the average abundance of juvenile fish in the Hudson River has declined—60% for river herring, 69% for Atlantic tomcod, and 59% for white perch—and juvenile striped bass survival has declined 87%. These declines coul...

Historically, the fisheries for adult river herring (i.e., alewife Alosa pseudoharengus and blueback herring A. aestivalis) and American shad A. sapidissima were economically important in Albemarle Sound, North Carolina. Stocks of these species are in decline, while stocks of striped bass Morone saxatilis have increased roughly 10-fold in the Albemarle Sound-Roanoke River since the early 1990s. The goal of this study was to quantify the predatory impact of age-1 striped bass on age-0 prey fishes by estimating striped bass consumption rates and comparing loss rates from predation with total prey loss rates using catch curves. Age-1 striped bass and their potential prey were collected with beach and purse seines from western Albemarle Sound from spring to fall, 2002 and 2003. Commercially and ecologically important prey in one or both years included river herring, American shad, Atlantic menhaden Brevoortia tyrannus, and yellow perch Perca flavescens. Predation by age-1 striped bass had a marked ef...

Adult blueback herring Alosa aestivalis (N = 116) were collected during the 1999, 2000, and 2002-2004 spawning runs from sites on the Hudson and Mohawk rivers, and gut contents were analyzed. Thirty-four fish (33% of those examined) were found to contain food material. Food items were present in 41% of Mohawk River samples and 11% of Hudson River samples; all Hudson River fish containing food were captured in small tributaries above the head of tide. Hudson River fish predominantly consumed zooplankton, while Mohawk River fish consumed benthic aquatic insects in large quantities, including Baetidae, Ephemeridae, and Chironomidae. Using stable isotope analysis and a mixing model, we found that fish collected later in the season had significantly decreased marine-derived C. Condition indices of later-season fish were equal to or greater than those of fish collected earlier in the season. Blueback herring in this system may face increased energy requirements as they migrate farther upstream during s...

American shad Alosa sapidissima, hickory shad A. mediocris, and blueback herring A. aestivalis spawn in Florida's St. Johns River during winter and spring, and juveniles migrate out of the estuary during the following fall. We assessed the temporal trends of juvenile relative abundance and size as each species moved downstream past Palatka, Florida, and compared these values to historical data from the system. Juveniles were collected from April 2004 to March 2005 primarily with surface trawling at night and with supplemental daytime electrofishing. Relatively few juveniles were collected by trawl (23 American shad, 7 hickory shad, and 36 blueback herring) or by electrofishing (55 American shad, 4 hickory shad, and 179 blueback herring). Trawl catch rates were highest in autumn, and electrofishing catch rates were highest in autumn and early winter. Both sampling methods caught juveniles at similar sizes. The surface trawl catch rates of juvenile American shad in 2004 and 2005 were not significan...

Seasonal distribution, abundance, habitat use, hatch dates, growth, and mortality of larval blueback herring Alosa aestivalis and alewife A. pseudoharengus were studied in the Roanoke River watershed, downstream from the Roanoke Rapids Dam in North Carolina. Ichthyoplankton was sampled from man-made canals, a creek, an oxbow, a flooded bottomland hardwood forest, the main river channel, and along the river's edge. To identify larval clupeids, we developed a dichotomous key for clupeids found in the study area using morphometric, meristic, and pigmentation characters synthesized from the literature. Distribution, abundance, and back-calculated hatch dates of larvae and eggs were used to describe spawning period, spawning habitat, and nursery habitat. Blueback herring and alewife eggs and larvae were present from early April through late May. Based on the presence of eggs and early-stage larvae, both species spawned in backwater tributary systems, including flooded bottomland hardwood forests. Our ...

J. Strom Thurmond Lake (Georgia-South Carolina) strongly stratifies during the summer, producing a temperature-dissolved oxygen “squeeze” for landlocked blueback herring Alosa aestivalis. A coupled Eulerian-Lagrangian hybrid (CEL hybrid) model was developed to improve understanding of and better predict the in-reservoir movements of blueback herring in response to these limiting conditions. An existing application of CE-QUAL-W2, a two-dimensional, laterally averaged water quality and hydrodynamic model, was used to simulate the spatial and temporal dynamics of summer water temperature, dissolved oxygen, and hydraulics. The biological module was parameterized by using mobile hydroacoustic survey data supplemented with species composition data from gill-net surveys. The simulation accurately described the longitudinal (r 2 = 0.67) and vertical (r 2 = 0.93) distributions observed for blueback herring. The model results suggest that the longitudinal distribution of blueback herring in summer is best ...

Many populations of anadromous herring, (e.g., alewives Alosa pseudoharengus and blueback herring A. aestivalis, collectively referred to as river herring) are in decline. To help understand the various processes influencing their relative abundance, we studied juvenile river herring populations in 11 small, coastal Massachusetts systems. We examined diel and seasonal movements, variation in patterns of abundance, and relationships between juvenile river herring numbers and seven abiotic and biotic factors (stream discharge, pond temperature, habitat availability, pond transparency, pH, food availability, and spawning stock size). Seasonally, juvenile downstream migration peaked in early summer, and most juvenile river herring emigrated between 1200 and 1600 hours. Little or no emigration occurred in late summer when stream channels were often dewatered, although several streams experienced a smaller, more variable emigration peak in the fall. In univariate regressions, stream discharge, pond vol...

Juvenile anadromous river herring (alewife Alosa pseudoharengus and blueback herring A. aestivalis) spend the first 3 to 7 months of life in headwater lakes of coastal systems. Systems that support herring often produce trophy largemouth bass Micropterus salmoides. Even though biologists, managers, and anglers have speculated about the value of anadromous herring as a key prey for resident predators, the contribution that herring make to the diets of these predators has not been assessed. Herein, we quantified largemouth bass diets in two coastal lakes, Santuit and Coonamessett ponds, that contained anadromous herring, and we used bioenergetics modeling to evaluate the importance of herring prey to largemouth bass growth. During May through November 1994, largemouth bass diets consisted of various fish species, crayfish, and other invertebrates. Although not the most important prey overall, herring were the most important fish prey consumed in both lakes based on number of individuals consumed. I...

We examined the diets of 374 age-0 bluefish Pomatomus saltatrix collected in the Hudson River estuary from July to October 1989. Fish were the primary prey, accounting for 96–99% of the diet by weight. Anadromous fishes, including striped bass Morone saxatilis, blueback herring Alosa aestivalis, American shad Alosa sapidissima, and Atlantic tomcod Microgadus tomcod, constituted a large portion of the diet of bluefish of all sizes. There was a positive linear relationship between prey size and predator size, Small and medium-sized bluefish consumed mostly bay anchovies Anchoa mitchilli, striped bass, and white perch Morone americana, whereas the largest bluefish primarily preyed on Atlantic tomcod. Bluefish fed opportunistically on the most abundant prey (bay anchovies, striped bass, and white perch) but larger bluefish exhibited a preference for Atlantic tomcod. We also detected an ontogenetic shift in prey type that may have been determined by changes in the size and relative abundance of prey t...

Fecundity, ovary weight, and egg weights, adjusted for fish length, of anadromous alewives Alosa pseudoharengus and blueback herring A. aestivalis differed among some of four Maritime province rivers. Fecundity was poorly predicted by age. Spawning history (number of previous spawnings) did not affect fecundity and “fecundal senility” was not observed. Fecundity was usually higher for blueback herring than for similarly sized alewives. Reproductive condition (gonadosomatic index) of mature fish differed among rivers for both species. The time of sample collection influenced gonadosomatic index values for blueback herring but not for alewives. Gonadosomatic index values of alewives and blueback herring were uncorrelated with an index of distance upstream × elevation of the sampling site. Two major egg size-groups occurred in mature ovaries of both species. The largest egg size-group consisted of eggs ripening for spawning; the smallest size-group was retained after spawning. Fertility, as a percen...

Large numbers of spawning, anadromous clupeid fish (Alosa spp.) ascend North American coastal rivers and streams annually. In many regions, post-spawning mortality is high, resulting in potentially significant inputs of marine-derived animal detritus to tidal and nontidal freshwater systems. I estimated retention of carcasses and assessed the mechanism(s) of biological processing for carcasses of migratory blueback herring Alosa aestivalis in the James River, Virginia. In a first experiment, 418 tagged and weighed carcasses placed in the river were transported downstream at an average rate of 986 m/h. In a second experiment, 72 carcasses were fixed in the river as artificial substrates and recovered over the next 192 h. Instantaneous decomposition rates averaged 0.015/h, and the predicted mean time to complete decay was more than 240 h. An aquatic saprolegniale fungus (Saprolegnia sp.) heavily colonized most carcasses after 48 h. No aquatic macroinvertebrates were associated with any recovered ca...

Threadfin shad Dorosoma petenense and blueback herring Alosa aestivalis were introduced into Jocassee Reservoir, South Carolina, in the early 1970s as prey for large piscivores. To assess the potential for trophic competition between these clupeids, we examined their diets and the extent of diet overlap in May, August, and December 1982 and February 1983. The diet of blueback herring consisted mainly of large species of cladocerans and copepods supplemented in August with Chaoborus punctipennis and young fish. Mean length of the organisms eaten by blueback herring was 1.4 mm. Threadfin shad fed on smaller species of cladocerans and copepods, as well as on rotifers and copepod nauplii. The mean length of the organisms eaten by threadfin shad was 0.4 mm, which differed significantly from the mean length of the zooplankton population in Jocassee Reservoir (0.6 mm). Phytoplankton contributed 24 and 32% of the stomach contents of threadfin shad in August and December. Bosmina longirostris was importan...

During 1966 and 1967, the spawning runs of an anadromous population of alewives, Alosa pseudoharengus (Wilson), were studied in Bride Lake, Connecticut. Alewives entered the lake from Long Island via Bride Brook from March to June. The number of fish entering the lake each day varied and was not related to water temperature or amount of moonlight. Males predominated among early migrants, whereas a 1:1 sex ratio existed through the later part of the migration. The average size of adults decreased as the migration progressed. Adults spent from several days to 3 months on the spawning grounds, the males outnumbering the females. Counts of the number of fish entering and leaving the lake indicated that high mortalities occurred. Females spawned from 48,000–360,000 eggs. The total number of eggs spawned in the lake was estimated to be 2.0 X 1010. Young alewives migrated seaward from June to October and increased water flow was thought to be a major stimulant. One young alewife migrated seaward for eve...

Trawl catches indicated diel migratory activities by young-of-the-year alewife Alosa pseudoharengus, American shad A. sapidissima, and blueback herring A. aestivalis in Virginia rivers. Bottom catches were significantly greater during day than at night; conversely, surface catches were significantly greater at night than during day. Spatial separation of alewife and blueback herring stocks, which could reduce feeding competition, also was indicated. Surface pushnet catches of blueback herring were associated with a sky-opacity index, suggesting that this species (or its prey) is negatively phototropic. The influence of light on distributions of juvenile Alosa should be taken into account when sampling location, time, and gear are chosen for stock-assessment programs.

Blueback herring (Alosa aestivalis) were first detected near the mouth of the Connecticut River on April 13, 1966, April 18, 1967, and April 19, 1968, when water temperatures were 7.8, 4.7, and 9.4 C, respectively. Spawning was first observed when stream temperature was 14 C. Abundance in the river was greatest from mid-May to mid-July, but smaller spawning groups were observed in late April and mid-September. Blueback herring preferred a swift stream flow and hard substrates for spawning sites, and to a great degree were spatially isolated from spawning alewives. Both sexes were present in age classes III through VII; age V was the modal class for each sex. In the spawning areas there was a 2:1 sex ratio of males to females. Males were more abundant in age classes III, IV, and V; there was equal abundance in age class VI, but females dominated age class VII. Fecundity was related to total fish length up to about 300 mm, but declined in larger females.

Immediate mortality of juvenile alosids, American shad Alosa sapidissima and blueback herring A. aestivalis, passed through the 17-MW Kaplan turbine at Holyoke Dam on the Connecticut River was estimated with mark-capture methods. Turbine-induced mortality was 62% at 16.5-MW generation, 82% at 12 MW, and 82% at 5.5 MW. The significantly lower mortality of fish at full power output is thought to be related to greater turbine efficiency. Received February 29, 1984 Accepted February 28, 1985

Food-habit, niche-breadth, and diet-overlap analyses were conducted for larvae of American shad Alosa sapidissima and blueback herring Alosa aestivalis collected from the Connecticut River from June 3 to July 15, 1981. River zooplankton densities (numbers˙m−3 were used to assess the influences of prey availability on niche-breadth and diet-overlap indices for the species. Niche-breadth values were consistently higher for blueback herring than for American shad larvae. American shad fed mostly on the less-abundant crustaceans and immature insects, whereas blueback herring larvae usually utilized the numerically dominant rotifers. The cladoceran Bosmina sp. was utilized extensively by American shad of all sizes and by 13–16-mm blueback herring larvae, and was the only prey for which interspecific competition between the larval predators might occur. The mean mouth gape of American shad larvae was always larger than that of blueback herring larvae at a given length, and American shad larvae of all s...

Summer nighttime abundance and localized distribution of fishes in a tidal cove were studied by beach seining for comparison with a previous daytime study. American eels were relatively abundant at night and absent during the day. Alewife, blueback herring, and Atlantic silver-side were more abundant in the cove at night. Although mummichog numbers were greatly reduced at night, they remained an important constituent of the night fauna. Lesser components of the night fauna included Atlantic herring, Atlantic tomcod, smooth flounder, winter flounder, and rainbow smelt.

The fall downstream migrations of juvenile American shad Alosa sapidissima and blueback herring Alosa aestivalis were monitored for 3 years in the Connecticut River at Holyoke Dam, Massachusetts. Decreasing water temperature—not increasing river flow—determined the time migration began and ended for both species. The migration of blueback herring began in September as water temperature declined to 21°C, peaked at 15–14°C, and ended in late October or early November at 10°C. The American shad migration began at 19°C, peaked at 14–9°C, and ended at 10–8°C. Most movement peaks were centered on quarter-moon periods; seven were centered on a new moon and none was centered on a full moon. The diel pattern of migration varied among the 3 years. In general, however, blueback herring were active throughout the 24-h period (peak activity at 1800 hours), and American shad moved in the afternoon and evening (peak activity between 1800 and 2200 hours). The migration of juvenile American shad may be mediated b...

Age-0 striped bass Morone saxatilis were fed one of three formulated diets containing 34%, 44%, or 55% crude protein or a blueback herring Alosa aestivalis reference diet. Striped bass fed the 55% crude-protein formula diet had the highest average weight gain and feed efficiency. Protein efficiency ratio and protein retained were highest in striped bass fed the 34% crude protein diet. Whole-body protein concentration was unaffected by dietary protein concentration. Whole-body moisture increased, and whole-body lipid decreased, with increasing dietary protein concentration. Striped bass whole-body lipid concentration was negatively correlated with whole-body moisture concentration within each dietary treatment.

Eggs of striped bass (Morone saxatilis), white perch (M. americana) and blueback herring (Alosa aestivalis) were exposed to a series of total residual chlorine (TRC) concentrations until hatch occurred. Larval development of the three species was inhibited by increasing TRC concentrations. Length of larval fish at hatch decreased with increasing TRC concentrations and the production of abnormal blueback herring larvae increased with increasing TRC concentrations.

Whole body concentrations of Cd, Cr, Cu, Fe, and Zn were determined for samples of chain pickerel (Esox niger), bluegill (Lepomis macrochirus), blueback herring (Alosa aestivalis), brook silverside (Labidesthes sicculus), and golden shiner (Notemigonus crysoleucas) from a 1,120-hectare impoundment near Aiken, South Carolina. Species differences in mean concentrations were found for all five elements. Frequency distributions of 23 species-element groupings were compared to the normal, lognormal, Weibull, and exponential distributions. The lognormal, normal, Weibull, and exponential distributions had the best fit to 57, 17, 26, and 0 percent of the species-element groupings, respectively. Four of the 23 species-element groupings departed significantly from all four of the distributions, primarily as a result of strong positive skewness. All species for which Cd and Cr were studied exhibited significant positive skewness, while skewness was less pronounced for concentrations of Cu, Fe, and Zn. Most ...

We measured the sensitivity of eggs and yolk-sac larvae of blueback herring Alosa aestivalis to acid and aluminum pulses in moderately soft fresh water (23–25 mg/L, hardness as CaCO3) during 96-h experiments in the laboratory. Over a 3-h period, pH was reduced from 7.4–7.7 to 5.5–5.6, coincident with an increase in aluminum from 0 to 0.10, 0.15, 0.20, or 0.25 mg/L. These pH-aluminum conditions were maintained for five single-pulse durations (0.5, 4, 8, 12, 24 h) and then gradually returned to control conditions within 8–10 h. Relatively mature embryos (20–24 h postfertilization, early tail-bud stage) were more tolerant than larvae to all treatments. Eggs exposed to a 24-h pulse of pH 5.5–5.6 and 0.20 mg/L total aluminum (predicted total monomeric aluminum, 0.09 mg/L) experienced the highest mortality observed for this life stage, 48%. Larvae tolerated single pulses of pH 5.5–5.6 (without aluminum) for up to 12 h, but mortality doubled (25% to 49%) when pulse duration doubled (12 h to 24 h). Pulse...

Blueback herring (Alosa aestivalis) comprised 79%, alewife (A. pseudoharengus) 16%, and American shad (A. sapidissima) 4% of the juvenile Alosa taken in 221 bottom trawl collections made during December-April from 1972 to 1975 in coastal, southern New Jersey waters. Most of these fishes were less than 100–120 mm FL. All three species were most numerous in March. Coastal waters out to at least 8 km offshore provide a continuum of estuarine conditions favorable for overwintering by these fishes.

A direct relationship existed between standing crops of zooplankton and distribution, growth, and feeding of young-of-the-year blueback herring, Alosa aestivalis, in the James River, Virginia. Zooplankton densities were highest upstream where food consumption and growth rates were correspondingly highest. A progressive downstream decrease and upstream increase in fish abundance occurred during the study. Condition (K) decreased after flooding from Hurricane Camille. Blueback herring fed primarily on copepods (Eurytemora affinis, Cyclops vernalis, and Canthocamptus robertcokeri), but cladocerans (Bosmina sp. and Diaphanosoma brachyurum) were also important. Selection (electivity) was strongest for adult copepods and weakest for copepod nauplii. Selection for copepodites and Bosmina sp. was moderate to weak. Feeding occurred only during daylight. Predation on copepods and copepodites by blueback herring resulted in population dominance by the smaller Bosmina sp. Respiration experiments were carried...

Eggs and larvae of white perch (Morone americana), striped bass (Morone saxatilis), and blueback herring (Alosa aestivalis) and eggs of Atlantic silversides (Menidia menidia) and tidewater silver-sides (M. beryllina) were exposed to various residual chlorine levels for preestablished periods. Almost all LC50 values fell between 0.20 to 0.40 ppm of total residual chlorine for eggs, and between 0.20 to 0.32 ppm for larvae. Age-related effects in sensitivity to chlorine were observed. Abnormal larvae issued from blueback herring eggs exposed to low chlorine concentrations.

During 1966 and 1967, scales from 1,125 anadromous alewives, Alosa pseudoharengus, were collected from the Connecticut River and Bride Brook, Lyme, Connecticut. Scales from 722 blueback herring, Alosa aestivalis, were collected from the Connecticut and Thames rivers during the same period. Scales were read and interpreted for total age. Questionable annuli were interpreted by determining the average distance between annuli and the average and range of the number of transverse grooves per annulus. Most scales of both species were found to have zones reflecting habitation of freshwater (freshwater zones). Freshwater zones were broader on blueback scales, and occurred 44% more often than on alewife scales. The relationship between body and scale lengths was calculated for both species and was found to be linear and highly correlated. Alewives reached a maximum age of eight years, while bluebacks reached seven years. Age II and III alewives were never collected. The majority of alewives in the spawni...

Fifteen species of pelagic fishes were collected in 156 gill net sets at eight locations in the Sheepscot River-Back River estuary, Wiscasset, Maine, June 1970 through December 1971. Highest catches occurred June through August. Only the rainbow smelt is a year-round resident. Differences in abundance in space and time are apparently related to temperature. During the summer, alewives, blueback herring, and Atlantic menhaden were most abundant in the relatively warm Back River estuary, while Atlantic herring, Atlantic mackerel, and spiny dogfish were most abundant in the more oceanic Sheepscot River estuary. Prolonged near-freezing temperatures apparently limit the time pelagic fishes spend in the estuary and limit the number of species which can inhabit it. It is hypothesized that the distribution of pelagic species which exhibited preferences for colder water, such as Atlantic herring, would be most affected by artificial warming of the surface waters of the Back River estuary, if a new atomic ...