Search

We analyzed four decades of presence–absence data from a fishery-independent survey to characterize the long-term phenology of river herring (alewife, Alosa pseudoharengus; and blueback herring, Alosa aestivalis) spawning migrations in their southern distribution. We used logistic generalized additive models to characterize the average ingress, peak, and egress timing of spawning. In the 2010s, alewife arrived to spawning habitat 16 days earlier and egressed 27 days earlier (peak 12 days earlier) relative to the 1970s. Blueback herring arrived 5 days earlier and egressed 23 days earlier (peak 13 days earlier) in the 2010s relative to the 1980s. The changes in ingress and egress timing have shortened the occurrence in spawning systems by 11 days for alewife over four decades and 18 days for blueback herring over three decades. We found that the rate of vernal warming was faster during 2001–2016 relative to 1973–1988 and is the most parsimonious explanation for changes in spawning phenology. The influence of a shortened spawning season on river herring population dynamics warrants further investigation.

Nontarget catch restrictions are becoming common in fisheries management. We test a potential tool for reducing nontargeted catch that combines species’ distribution models and ocean forecast models. We evaluated our approach for Atlantic herring (Clupea harengus), Atlantic mackerel (Scomber scombrus), alewife (Alosa pseudoharengus), and blueback herring (Alosa aestivalis). Catch of the latter two species is capped in commercial fisheries of the former two species. Ocean forecasts were derived from a data-assimilative ocean forecast model that predicts conditions 0–2 days into the future. Observed oceanographic conditions were derived from CTD casts and observed fish presence–absence was derived from fishery-independent bottom trawl collections. Species distribution models were used to predict presence–absence based on observed and forecasted oceanographic conditions, and predictions for both were very similar. Thus, most of the error in predicted distributions was generated by the species distribution models, not the oceanographic forecast model. Understanding how predictions based on forecasted conditions compare with predictions from observed conditions is key to developing an incidental catch forecast tool to help industry reduce nontarget catches.

Bycatch of mid-trophic-level anadromous fishes that connect marine and freshwater ecosystems is a growing conservation concern. Anadromous alewife (Alosa pseudoharengus) and blueback herring (Alosa aestivalis) are important components of coastal freshwater and marine food webs, but have experienced dramatic declines in the abundances of spawning adults. Freshwater-focused restoration efforts have yielded few consistent signs of recovery, raising concerns that bycatch in Northwest Atlantic commercial fisheries may be negating these conservation actions. Using data from 15 microsatellites genotyped for baseline populations and bycatch, we conducted genetic stock identification to understand how bycatch was partitioned among previously identified regional genetic stocks. We then combined this information with fishery observer data to estimate genetic stock-specific bycatch mortality for the southern New England Atlantic herring fishery (2012–2013). Bycatch overall, but especially in the Atlantic herring fishery, was disproportionately assigned to the most severely depleted genetic stocks (alewife southern New England stock — 70% of assignments; blueback herring mid-Atlantic stock — 78% of assignments). These genetic stocks overlap in the region surrounding Long Island Sound, suggesting that bycatch taken from this area in recent years may be negatively impacting recovery efforts in this region. Our study suggests that mitigating bycatch on the southern New England fishing grounds may benefit recovery efforts for alewife and blueback herring genetic stocks that have experienced the greatest declines in spawning adult abundances.

Understanding the location and duration of habitat use by young fish is important for management and restoration efforts, but is largely unknown in anadromous species. We used otolith microchemistry and ambient water concentrations of Ca, Ba, Mn, and Sr to identify habitat use in the first year of growth for 131 returning adult blueback herring (Alosa aestivalis) collected in seven spawning runs along the coast of Maine, USA. Ambient Sr:Ca ratios were correlated with salinity and were used as primary indicators of habitat use. Results revealed variable individual migration histories with several discrete migratory patterns; some fish migrated into seawater well before the end of the first year, while the majority exhibited longer residency in freshwater or low salinity habitat. Total area of available habitats ranged from approximately 213 to 6053 ha fresh water and 204 to 3395 ha estuary. Residency in freshwater or low salinity habitats was positively correlated with extent of freshwater habitat (r = 0.37, P < 0.001). Results emphasize the importance of conserving a variety of habitat types to maintain variation in life histories and ensure plasticity in migratory behavior of diadromous species.

The abundance of alewife (Alosa pseudoharengus) and blueback herring (Alosa aestivalis) has declined throughout their range, and there are increasing concerns about their conservation status. Because of their diadromous life history, variability in rates of survival in fresh water can affect overall recruitment. The objective of our study was to assess how river temperature and flow influence young of the year (YOY) river herring recruitment in the Northeast US. Observations of adult and juvenile fish in five rivers were used to construct spawner–YOY recruits models; these rivers were chosen because of the length of the time series (>15 years) and the paired observations of spawners and juveniles. An environmentally explicit stock–recruitment model explained a substantial fraction (41% to 80%) of the variance in YOY abundance, depending on river system. Our approach allowed for a preliminary discussion of potential mechanisms, which need to be further substantiated by focused field and laboratory studies. Early summer river flow and river temperature had the greatest influence, indicating the importance of conditions in nursery habitats. In certain systems, spring or fall conditions were also important determinants of survival, suggesting additional effects of the environment on spawning of adults and juvenile egress from freshwater nursery habitats.

We compared the accuracy of different combinations of natural markers, specifically otolith elemental (Sr:Ca and Ba:Ca) and isotopic ratios (87:86Sr) with and without genetic stock constraints to evaluate their ability to distinguish among anadromous river herring (i.e., alewife, Alosa pseudoharengus, and blueback herring, Alosa aestivalis) populations from their US ranges. Model accuracy increased when constrained to a regional level by genetic stocks. Both species were misclassified to sites up to 1000 km from their collection location when only otolith chemistry was used. The inclusion of genetic constraints improved reclassification rates, and the longer time scale of genetic variation makes this method less sensitive to interannual variation. We recommend the combined approach of otolith chemistry and genetics as a means to trace river herring in marine bycatch back to river of origin.

The ability to traverse barriers of high-velocity flow limits the distributions of many diadromous and other migratory fish species, yet very few data exist that quantify this ability. We provide a detailed analysis of sprint swimming ability of six migratory fish species (American shad (Alosa sapidissima), alewife (Alosa pseudoharengus), blueback herring (Alosa aestivalis), striped bass (Morone saxatilis), walleye (Stizostedion vitreum), and white sucker (Catostomus commersoni)) against controlled water velocities of 1.5–4.5 m·s–1in a large, open-channel flume. Performance was strictly voluntary: no coercive incentives were used to motivate fish to sprint. We used these data to generate models of maximum distance traversed, taking into account effects of flow velocity, body length, and temperature. Although the maximum distance traversed decreased with increasing velocity, the magnitude of this effect varied among species. Other covariate effects were likewise variable, with divergent effects of temperature and nonuniform length effects. These effects do not account for all of the variability in performance, however, and behavioral traits may account for observed interspecific differences. We propose the models be used to develop criteria for fish passage structures, culverts, and breached dams.

The parasite fauna of blueback herring (Alosa aestivalis) and alewife (Alosa pseudoharengus) were examined to determine their usefulness as biological indicators in the differentiation of these two sympatric species. Thirteen parasite species were identified from 100 specimens each of blueback herring and alewife from the main estuary of the Miramichi River, New Brunswick, of which 11 and 8, respectively, represent new host records. Significant differences (p

Using vertical polyacrylamide electrophoresis and autoradiography we have shown that blueback herring, (Alosa aestivalis), is polymorphic for transferrins found in the plasma. Assuming a three-allele, one-locus system, the frequencies of the transferrin bands agree with the Hardy-Weinberg model. Of the four samples analyzed, two were similar in transferrin frequencies but these were different from the other two. We conclude that transferrin is of limited suitability as a population marker in the case of blueback herring resident in the St. John River, New Brunswick.

For the alewife (Alosa pseudoharengus) and blueback herring (Alosa aestivalis) total lipid content was neither size nor sex specific. The lipid content of alewife and blueback herring from the LaHave River, Nova Scotia, was similar at 7.6 and 7.0%, respectively. However, in samples from the Margaree River there was a significant difference in lipid content between alewife and blueback herring (7.8% vs. 5.4%, respectively). The difference appeared to be a consequence of water temperature since late migrants of both species had a significantly lower lipid content. For alewife migration in the LaHave River, a distance of 31 km, lipid content declined by 22%, whereas in the Margaree River lipid loss was 18% over 32 km. Lipid content was also dependent on reproductive maturity, with lipid levels of 14.4, 8.7, and 5.4% in immature, prespawning, and spent alewife from site 1 on the Margaree River. Immature fish were characterized by a very high lipid content associated with the visceral organs. Protein utilization was not evident in the prespawning migration of alewife from the LaHave River. Based on lipid depletion the migration energetics of alewife in the two rivers were similar at 21.68 and 18.53 kJ∙kg−1∙km−1 in the LaHave and Margaree Rivers, respectively.

The male and female of Clavellisa cordata Wilson, 1915 are described from the gills of blueback herring (Alosa aestivalis), alewife (Alosa pseudoharengus), and American shad (Alosa sapidissima) collected in New Brunswick. The female differs from the original description in the presence of uropods, the apical armature of the first antennae, second antennae, and first maxillae, the presence of secondary teeth on the mandibles, and several additional processes on the maxillipeds. The male differs in the presence of uropods and in the detailed morphology of the various appendages, in particular the maxillipeds. Distinctive features of Clavellisa spinosa, another species occurring in the northwestern Atlantic, are briefly discussed. Differences between Clavellisa cordata and a closely related species, Clavellisa emarginata, occurring in the northeastern Atlantic, are listed. The present redescription of Clavellisa cordata represents a northern range extension and three new Canadian host records.

Significant heterogeneity occurred in the spatial and temporal pattern of the nocturnal, near-surface (0 to 1.5 m depth) density of juvenile anadromous alewife (Alosa pseudoharengus) and blueback herring (A. aestivalis) in the Mactaquac Dam headpond, Saint John River, New Brunswick. Juvenile alewife were less available to a pushnet than were blueback herring. Patches of higher density persisted for up to 4 wk for both species. Estimates of patch size depended upon the sampling scale, with larger patches (16 to 58 km long) composed of smaller patches (0.5 to 2.2 km long). The index of aggregation of Taylor's power law was similar for both species pooled value 2.20) Lloyd's index of patchiness varied significantly, for both species, spatially but not temporally, and tended to be higher for blueback herring than for alewife. Density and patchiness differed for both species within and between an upriver, lotic zone and downriver, lentic zone. Mean densities were more precisely estimated at high than at low densities and for alewife than for blueback herring (n = 61). Stratification increased the precision, relative to simple random sampling, of estimates of mean density, particularly at high densities of the more patchily dispersed blueback herring. Autocorrelation occurred in the spatial density pattern of both species at coarse (1–100 km) and medium (0.1–4 km) sampling scales. Variations in the intensity and grain of patchiness may affect the choice of survey design, sample and sample unit size, and frequency of sampling required for a desired precision of density estimates.

Studies of zooplankton feeding by juvenile blueback herring (Alosa aestivalis), an obligate planktivore, and juvenile bluegills (Lepomis macrochirus), a facultative planktivore, indicate that they search by markedly different methods. The herring searches as it swims, sighting most prey above its horizontal course, and swims up to take the prey. The bluegill searches while stopped (hovering). If a prey is sighted, it swims to it, sucks it in, then coasts to a stop to resume searching. If no prey is sighted, it swims a short distance, coasts to a stop, and searches again. For uniform size prey (Artemia salina first instar nauplii) the time the bluegill hovers in a particular search position is positively correlated with the distance the prey is from the fish (r2 = 0.69–0.77, four fish). This, in conjunction with previous work on bluegills, suggests they take the first prey item seen, rather than choosing between prey. The bluegill is more reactive to moving prey of Daphnia size; however, blueback herring do not distinguish between motile and nonmotile prey, perhaps because any prey's image is moving across its retina as the herring swims. Stopping to search may be adaptive where there is a heterogenous (weedy) background, whereas moving prey are detected against the stationary background. Such a background is likely confusing to a moving fish.Key words: blueback herring, Alosa aestivalis; bluegiil, Lepomis macrochirus; predation, zooplankton

Most of the young fish of nine species that were entrained in the condenser cooling-water system of the Connecticut Yankee nuclear power plant were dead by the time they reached the lower end of the plant’s 1.83-km (1.14 mile) long discharge canal. Sampling during June and July, when 95% of the nonscreenable fish were abundant near the plant’s intake, showed that approximately 80% of the mortality in the canal was caused by mechanical damage and 20% was attributed to heat shock and prolonged exposure to temperatures elevated above 28 C. There was no measurable mortality due to the injection of sodium hypochlorite into the system as a biocide. The number of nonscreenable living fish entrained at the intake averaged about 4% (range, 1.7–5.8%) of those passing by the plant under conditions of unidirectional net tidal flow.

This study reviews methods formerly recommended for discriminating between the alewife (Alosa pseudoharengus) and blueback herring (A. aestivalis) and suggests an alternate, more efficient, external species-specific character. The method relies on differences in scale imbrication patterns and scale morphology.Key words: alewife, Alosa pseudoharengus; blueback herring, A. aestivalis; morphology, meristics, identification

Differences in the morphology of the otoliths of Alosa pseudoharengus (alewife) and Alosa aestivalis (blueback herring) have been found to be reliable criteria in distinguishing the two species.