The role of ``conservatism' in herring migrations

Herring (Clupea harengus) migrationstend to remain constant over periods of severalyears or even decades, despite environmentalvariation. When a migration pattern is changed,apparently in response to an environmentalstimulus, the change in migratory behaviorsometimes lasts longer than the environmentalstimulus itself. This paper reviews evidencethat the response of herring to environmentalchange is restrained by conservatism. Herringapparently develop certain migratory habitsduring the early stage of adult life and tendto adhere to these habits for life, even whenthe environment changes. Two elements ofconservatism are distinguished: the formationof habits within one generation, and thetransfer of habits between generations. Anumber of case studies on North Sea herring andNorwegian spring spawning herring are reviewedin order to find evidence for habit formationand tradition in the migrations of thesepopulations. By eliminating the possibilitythat homing to spawning, wintering and feedinggrounds is due to innate behavior orenvironmental constraints, it is shown that thereturn of these fish to the same areas eachyear is most likely a form of learned behavior.In many cases, new year-classes adopt the samemigration pattern as their predecessors, whichis explained by the social transfer of habitsfrom old herring to young ones. A change ofmigration pattern is usually initiated by arecruiting year-class that lacks the ``guidance'of older herring at the time it has to startits first migration. This may be the effect ofa special environmental condition that affectsthe distribution of the recruiting age groupmore than that of the adult stock component, andthereby results in a separation of the twostock components. After the recruitingyear-class has adopted the new migration route,it tends to repeat it in subsequent years. Thenew migration thus becomes habitual. Subsequentgenerations may copy the migration and continuethis behavior even after the originalenvironmental cause has disappeared.     

A simple vertical gill net system for variable current conditions

A new technique for suspending vertical gill nets is described. The system is designed to minimize the effects of currents, which otherwise could lift the lead line off the bottom or pull the floating line down.For more than two years, 30 m deep gill nets have been used in a Baltic Sea coastal region and have been found to work well in current, wave and wind conditions characteristic of this area. Setting a net takes about 5 minutes and retrieving it 10 minutes, even under relatively windy conditions (10–15 ms^–1). No special equipment is required to set or to haul a net, and we have used a variety of boats, from a small rowing boat to a 16 m long research vessel. The total material cost per net is about US $100.     

Duration of synchronous cleavage cycles and rate of development at different temperatures in the Baltic herring

The duration of one synchronous cleavage cycle (τ₀) in Clupea harengus membras at different temperatures ( T ) was given by: (logτ₀)= 2.4349–0–0684T for T= 0.9–13°C, and (logτ₀)= 1.61010–oooit for t= 13–18–7°C.     

Behavioural differences in starving herring Clupea harengus L. larvae correlate with body levels of essential fatty acids

Twenty days after hatching, a single stock of Atlantic herring ( Clupea harengus L.) larvae, cultured in the presence of rotifers and Artemia nauplii but showing little or no active feeding behaviour, displayed clear signs of starvation. Three groups of fish were distinguished: group I was generally pinhead-shaped, tended to swim with a spinning motion and floated vertically; group 2 lay moribund on the bottom of the tank; group 3 showed normal, active swimming behaviour. Fatty acids of total lipid extracted from groups 1 and 2 differed from group 3 in having markedly reduced percentages of 20:5n-3, 22:6n-3, 20:1 and 22:1. We conclude that individuals within a single stock of cultured herring larvae respond differently to starvation and that this generates well defined behavioural differences which correlate with levels of n-3 polyunsaturated fatty acids (PUFA) in body lipid. The implications of these observations are discussed.     

DIET OF HARBOR PORPOISES IN THE KATTEGAT AND SKAGERRAK SEAS: ACCOUNTING FOR INDIVIDUAL VARIATION AND SAMPLE SIZE

Stomach contents of 112 bycaught harbor porpoises ( Phocoena phocoena ) collected between 1989 and 1996 in the Kattegat and Skagerrak seas were analyzed to describe diet composition and estimate prey size, to examine sample size requirements, and to compare juvenile and adult diets. Although porpoises preyed on a variety of species, only a few contributed substantially to the diet. Atlantic herring ( Clupea harengus ) was the dominating prey species for both juveniles and adults. Our results, in combination with those from previous studies, suggest that where herring is a dominant food source, porpoises prey primarily on size classes containing mature or maturing individuals. Further, we also show that Atlantic hagfish ( Myxine glutinosa ) may be an important food resource, at least for adult porpoises. Examination of sample size requirement showed that, depending on the taxonomic level used to describe the diet, a minimum of 35–71 stomachs are needed to be confident that all common prey species will be found.     

Synthesis of Novel Isocytosine Pseudonucleotide Analogues

Abstract

Ethyl dialkylphosphonoacetates were prepared from the corresponding dimethylalkylphosphites via the Arbuzov reaction with ethyl bromoacetate. The phosphonoacetates so produced were converted into enaminoacetates by reaction with DMF dimethylacetal and these were used as bidentate electrophiles for the synthesis of phosphonopyrimidones. Several of these compounds were tested for biological activity but none were found to possess antiviral activity.     

Study on the Interaction between the Inclusion Complex of Hematoxylin with β-Cyclodextrin and DNA

Ultraviolet-visible (UV-vis) spectra, fluorescence spectra, electrochemistry, and the thermodynamic method were used to discuss the interaction mode between the inclusion complex of hematoxylin with β-cyclodextrin and herring sperm DNA. On the condition of physiological pH, the result showed that hematoxylin and β-cyclodextrin formed an inclusion complex with binding ratio n_hematoxylin:n_{β-cyclodextrin} = 1:1. The interaction mode between β-cyclodextrin-hematoxylin and DNA was a mixed binding, which contained intercalation and electrostatic mode. The binding ratio between β-cyclodextrin-hematoxylin and DNA was n_{β-cyclodextrin -hematoxylin}:n_DNA = 2:1, binding constant was K^? _298.15K = 5.29 × 10⁴ L·mol^?1, and entropy worked as driven force in this action.     

Feeding ecology of mackerel and dietary overlap with herring in Icelandic waters

The Northeast Atlantic mackerel (Scomber scombrus) has been extending its summer feeding distribution north and west, including around Iceland, since around 2006. The objective of this study is to quantify the weight gain and total food consumption of mackerel and to evaluate the food competition between mackerel and herring (Clupea harengus) feeding in the marine ecosystem around Iceland during the summers 2009–2011. Mackerel feeding in Icelandic waters gained around 43% on average in weight during these summers. Based on swept-area abundance estimates of mackerel from an international survey in 2011 and available estimates of food conversion efficiency in mackerel, the weight gain in Icelandic waters in 2011 corresponded to a total consumption of around 3.4 (2.4?4.5) million tonnes. Overall, 98% of 2314 mackerel, 91% of 398 Icelandic summer-spawning herring and 96% of 424 Norwegian spring-spawning herring stomachs, collected over the summers 2009?2011, contained food. The mean weight of the stomach content of mackerel was higher than for herring in all the years. While the stomach content weight of mackerel was generally highest in southeastern and southwestern areas, it was highest for herring in western, eastern and northern areas. Analysis of stomach contents showed that Copepoda were the most important food of mackerel in most areas, while Copepoda and Euphausiacea were the most important food items for herring. Fish prey contributed a higher proportion in stomachs of mackerel than herring, although relatively low for both species.     

Variation in egg mass within two Atlantic herring Clupea harengus stocks

The main objective of this study was to investigate if egg size (mass) at spawning is invariant for Scotia-Fundy summer and autumn (SFSH) and Icelandic summer (ISSH) spawning herring Clupea harengus. Oocyte dry mass measurements for SFSH females collected in 2001 and ISSH females collected in 1999 and 2000 showed a large variation. Difference in egg dry mass among fish was found to vary by as much as twofold in each stock. For ISSH, variation in egg mass was also apparent from oocyte volume measurements made jointly with a histological examination of the ovaries. Approximately 20% of the variation in egg mass could be explained by maternal whole-body mass or total length, indicating that length or age composition in the stocks can potentially influence the recruitment success. This implies that fisheries management strategies should aim to maintain a broad range in age composition.     

A Regional Retrospective Assessment of the Potential Stressors Causing the Decline of the Cherry Point Pacific Herring Run

The Pacific herring stock that spawns at Cherry Point, northwest of Bellingham, WA, has undergone a dramatic decline in the last 20 years. The population decline corresponds with a collapse of the age structure. The Cherry Point area contains three deep water shipping piers, two refineries, an aluminum smelter, and urban development. The Cherry Point Aquatic Reserve was formed initially to protect the spawning habitat of the Cherry Point Pacific herring run. We conducted a retrospective assessment using the relative risk model (RRM) to investigate the causes of the current decline of the Cherry Point run. The RRM combines aspects of the weight-of-evidence (WoE) approach and other methods of establishing causality into a framework that deals with multiple stressors, uncertainty, and spatial scale.

An analysis of the Cherry Point Pacific herring age structure and population dynamics indicates that the loss of reproductive potential of the older age class fish was the population characteristic that led to the decline of the run. Exploitation, habitat alteration and climate change are the risk factors that contribute to the decline of the Cherry Point Pacific herring. The retrospective assessment identified the cyclic nature of climate change, as expressed by the warmer sea surface temperatures associated with a warm Pacific Decadal Oscillation (PDO), as the primary factor altering the dynamics of the Pacific herring. Other factors are ranked accordingly along with the associated uncertainty. Criteria for selecting alternative endpoints for managing the Cherry Point Aquatic Reserve are also provided.

The strengths of the retrospective RRM include its ability to combine a WoE and causality criteria with a multitude of stressors at a regional scale. The difficulties include how to deal with differences in the magnitude of effects, and expressing the uncertainty as distributions.