Diel differences in catches of Western Baltic Spring Spawning Herring Larvae (Clupea harengus)

Comparative night and day catches of herring larvae were taken during the Rügen-Herring-Larval-Survey (RHLS) in 2007 and 2008 in the Greifswalder Bodden which is the main spawning area of the Western Baltic Spring Spawning Herring. The quantities and the size composition of larvae caught during night and day were examined. During night more larvae were caught compared to the samples taken at daytime, especially with larvae larger than 25 mm. This indicates avoidance reactions, which increase with the developmental stage of the larvae. The differences of the night and day catches are relatively constant until a length of about 25 mm, thus the night/day effect does not influence estimations concerning larvae smaller than 25 mm (e.g. N20 index). There might be an impact on estimations for larger larvae due to the night/day effect. For further research other aspects like cloud coverage at night, phase of the moon, underwater visibility and turbidity should be taken into account. These aspects might influence the avoidance reactions.

Organ damage in Atlantic herring larvae as a result of ocean acidification

The dissolution of anthropogenically emitted excess carbon dioxide lowers the pH of the world's ocean water. The larvae of mass spawning marine fishes may be particularly vulnerable to such ocean acidification (OA), yet the generality of earlier results is unclear. Here we show the detrimental effects of OA on the development of a commercially important fish species, the Atlantic herring (Clupea harengus). Larvae were reared at three levels of CO2: today (0.0385 kPa), end of next century (0.183 kPa), and a coastal upwelling scenario (0.426 kPa), under near-natural conditions in large outdoor tanks. Exposure to elevated CO2 levels resulted in stunted growth and development, decreased condition, and severe tissue damage in many organs, with the degree of damage increasing with CO2 concentration. This complements earlier studies of OA on Atlantic cod larvae that revealed similar organ damage but at increased growth rates and no effect on condition.

Early-life-history profiles, seasonal abundance, and distribution of four species of Clupeid larvae from the northern Gulf of Mexico, 1982 and 1983

We present data on ichthyoplankton distribution, abundance, and seasonality and supporting environmental information for four species of coastal pelagics from the family Clupeidae: round herring Etrumeus teres, scaled sardine Harengula jaguana, Atlantic thread herring Opisthonema oglinum, and Spanish sardine Sardinella aurita. Data are from 1982 and 1983 cruises across the northern Gulf of Mexico sponsored by the Southeastern Area Monitoring and Assessment Program (SEAMAP). This is the first such examination for these species on a multiyear and gulfwide scale. Bioproflles on reproductive biology, early life history, meristics, adult distribution, and fisheries characteristics are also presented for these species. During the summer, larval Atlantic thread herring and scaled and Spanish sardines were abundant on the inner shelf <40 m depth), but were rare or absent in deeper waters. Scaled sardine and thread herring were found virtually everywhere inner-shelf waters were sampled, but Spanish sardines were rare in the north-central Gulf. During 1982, larval Atlantic thread herring were the most abundant of the four target c1upeid species, whereas Spanish sardine were the most abundant during 1983. On the west Florida shelf, Spanish sardine dominated larval c1upeid populations both years. Scaled sardine larvae were the least abundant of the four species both years, but were still captured in 25% of inner-shelf bongo net collections. Round herring larvae, collected February-early June (primarily March-April), were abundant on the outer shelf (40-182 m depth) and especially off Louisiana. Over the 2-year period, outer-shelf mean abundance for round herring was 40.2 larvae/10 m2; inner-shelf mean abundances for scaled sardine, Atlantic thread herring, and Spanish sardine were 14.9, 39.2, and 41.9 larvae/l0 m2, respectively. (PDF file contains 66 pages.)

Ecology of larval fishes and large zooplankton in the Keweenaw Current region of Lake Superior, with special focus on lake herring, Coregonus artedi

I assessed the influence of the Keweenaw Current and spring thermal bar on the distribution of larval fishes and large zooplankton in Lake Superior. In 1998 and 1999, samples were collected from inshore (0.2 – 3.0 km from shore) and offshore (5.0 – 9.0 km from shore) locations on three transects off the western coast of the Keweenaw Peninsula, Michigan. For larval fishes, density and size distribution patterns of lake herring (Coregonus artedi), rainbow smelt (Osmerus mordax), burbot (Lota lota), deepwater sculpin (Myoxocephalus thompsoni), and spoonhead sculpin (Cottus ricei) suggest a seasonal inshore to offshore movement. For zooplankton, seasonal warming appeared to be the major factor that limited planktonic catches of the primarily benthic Mysisrelicta and Diporeia spp., while simultaneously stimulated growth and reproduction of the cladocerans Daphnia spp., Holopedium gibberum, and Bythotrephes cederstroemi. In contrast, calanoid copepods as a group were abundant throughout the entire sampling season. The greatest abundances of zooplankton were generally encountered offshore, even for the cladocerans, which apparently expanded from inshore to offshore locations with seasonal warming. In 2000, sampling efforts focused on lake herring. Samples were collected from surface waters at 0.1 – 17.0 km from shore on two transects. Lake herring larvae were also reared in the laboratory from eggs in order to validate the use of otolith microstructure for aging. Increment deposition was not statistically different from a daily rate starting from 28 days after hatching, near the time of yolk-sac absorption, but larvae with lower growth rates could not be aged as accurately. In Lake Superior, lake herring tended to be slightly more abundant, larger, and older at inshore locations, but a dense patch of younger larvae was also encountered 7 – 13 km from shore. The distribution iiipatterns suggest that larvae were transported by prevailing currents into the study region, possibly from the more productive spawning regions in western Lake Superior. Growth rates were suppressed at offshore locations where temperatures were less than 8°C. These results indicate that lake herring larvae may be transported far distances from spawning concentrations by longshore currents, and water temperatures may largely control their growth.

Mehr Nachwuchs bei Nutzfischarten der Nordsee, ausser beim Kabeljau

Ninety-one half-hour tows with the Grande Ouverture Verticale bottom trawl (GOV), 111 hydrographic stations and 100 catches with the Methot-Isaac-Kidd Net (MIK) were this years’ contribution of “Walther Herwig III” to the IBTS in various areas of the North Sea. Preliminary results indicate that especially haddock and, to some extent, whiting and Norway pout generated an ample 1999 yearclass. Indices for herring are also well above last years’ index whereas the cod indices indicate no substantial improvement of the stock. Largest concentrations of herring larvae were found in Moray Firth and west of the Dogger Bank/The Gut area. Temperatures of the North Sea were found to be above the long term means: 1 Centigrade on the open sea and up to 3 Centigrades in coastal areas. This years’ “WH III” IBTS activities at sea were considerably hampered by rough weather

Schwacher Nachwuchsjahrgang 2000 des Herings in der westlichen Ostsee

Several fishery independent estimates of the year-class strength are necessary for the assessment and the management of the total fish stock. An index for the year-class strength of the spring spawning herring in the western Baltic Sea is estimated on the basis of larvae surveys in the most important spawning ground. The results of this year’s herring larvae survey indicate a weak year-class 2000.

Zur Optimierung des Laboraufwandes bei Heringslarvensurveys im Greifswalder Bodden

Since 1977 larvae surveys have been carried out in the Greifswalder Bodden and the Strelasund every year to estimate an index of the year-class strength for the western Baltic herring stock. Different methods have been used to minimize the very extensive analytical work in the laboratory since 1993. As a further possibility the use of the mean dry weight of the larvae was investigated. This method was applied successfully to estimate the number of eggs in cod gonads. 88 samples of herring larvae were analysed. These experiments show that the use of the mean dry weight of herring larvae is not suited to reduce the work in the laboratory, because the accuracy of the estimates is unacceptable.

Optimismus nur für Sprotte, Wittling und Stintdorsch

70 half-hour tows using a Grand Ouverture Verticale (GOV) and – for the first time for R.V. “Walther Herwig III” – 102 plankton stations with a special plankton net were this years’ German contribution to the International Bottom Trawl Survey (IBTS). Results show only for sprat, whiting, and Norway pout relatively good incoming year-classes whereas indices for cod, haddock, mackerel, and herring point at rather poor recruitment. Strongest herring larvae concentrations (< 50 larvae/haul) were observed in the Moray Firth area, on the Fladenground and off the Jutland coast. 75 hydrographic stations showed the water masses in the area of investigation to be vertically mixed and homogenous. However, temperatures measured were 0.5 K to 1 K above longterm means.

Das deutsche Larvenprogramm im Hauptlaichgebiet des Herings der westlichen Ostsee - eine Forschungsaufgabe von internationaler Bedeutung

The German larvae surveys in the main spawning area of the herring of the western Baltic Sea - an international important program. The article gives an overview over the German herring larvae surveys in the Greifswalder Bodden and Strelasund. This program is performed under ecological points of view annually in the main spawning area of the herring of the western Baltic Sea and delivers indices, which are well suited as independent estimates of the herring year-class strength.

Historie und aktueller Stand des Internationalen Heringslarvensurveys in der Nordsee

Since years the International Herring Larvae Survey Program (IHLS) is an important and internationally established survey program in the North Sea. The IHLS serves the calibration of stock abundance estimates based on information from the commercial fishery and the method of Integrated Catch Analysis (ICA) which is a specific derivate of the Virtual Population Analysis (VPA). Meanwhile the IHLS database has been transferred from Aberdeen to Kiel and it has been agreed that the Institut für Meereskunde Kiel should continue to maintain this database and provide the abundance indices to be utilized by the ICES Herring Assessment Working Group as one of the means for assessing the state of the herring stock in the North Sea. For establishing the calculation procedure at Kiel, it was necessary to optimize both, the survey design and the index calculation. This article gives an overview over the survey’s history, it’s geography, the sampling design, the information content of the IHLS data base and the various methods of calculating the different indices necessary for the calibration.

Die vertikale Verteilung von Heringslarven im Greifswalder Bodden

Kurzfassung Im Rahmen einer Bachelorarbeit wurde untersucht, ob die Larven des frühjahrslaichenden Herings der westlichen Ostsee im Greifswalder Bodden eine inhomogene vertikale Verteilung aufweisen, da in bisherigen Studien aufgrund der niedrigen Gewässertiefe des Boddens von hydrografischer Durchmischung und somit homogener Ichthyoplanktonverteilung ausgegangen wurde. Dazu wurden zwei Nullhypothesen überprüft, eine, die annimmt, dass Heringslarven allgemein im Greifswalder Bodden homogen verteilt sind, eine zweite, nach der auch verschiedenen Längenklassen der Heringe homogen verteilt sind. Die Proben, die Mitte April an drei verschiedenen Stationen im Greifswalder Bodden genommen wurden, zeigten signifikante Unterschiede der Larvenabundanzen allgemein zwischen den beprobten Tiefenstufen als auch der Längenklassen zwischen den Tiefenstufen, sodass beide Nullhypothesen abzulehnen sind. Eine homogene Verteilung der Heringslarven kann ausgeschlossen werden. Abstract Larvae of the Western Baltic Spring Spawning Herring were sampled in the Greifswalder Bodden in the course of a Bachelor Thesis to investigate whether they are inhomogeneously vertically distributed. Previous research assumed homogeneous vertical distribution because of the shallowness of the Greifswalder Bodden due to hydrographical mixing of the water and the ichthyoplankton. Two null hypotheses were tested, one which presumes even vertical distribution of the herring larvae and another which presumes even vertical distribution within different length classes in the Greifswalder Bodden. Sampling took place at three different stations in the Greifswalder Bodden during April and results showed significant differences of the larvae abundances between the sampled depths and also significant differences of the length classes between the sampled depths. Therefore both null hypotheses can be rejected and a homogeneous vertical distribution of the herring larvae in the Greifswalder Bodden can be excluded.

Shrinkage of Gobiocypris rarus, Procypris rabaudi, and Sinilabeo rendahli preserved in formalin

Length measurements of preserved fishes are necessary in many types of fish surveys because logistics often do not allow for fish measurement immediately after catch. If the fixative causes significant shrinkage, then the preserved lengths cannot be directly used to indicate accurate live lengths. The objective of this study was to determine how preservation in formalin affects standard length of Gobiocypris rarus larvae (24-day-old and newly hatched), larval Procypris rabaudi (4-day-old), and larval Sinilabeo rendahli (12-day-old). Fishes were measured (to nearest 0.01 mm) and individually fixed in the appropriate formalin solution (2.5% or 5.0% formalin), then re-measured at 0.5, 1, 3, 7, 14, 30, 45 and 75 days after preservation to follow the time course of shrinkage. Most of the shrinkage occurred within the first half day after preservation. The 5.0% formalin caused a higher relative shrinkage rate than did the 2.5% solution; however, the difference was not statistically significant. In G. rarus, initial shrinkage of newly hatched larvae was higher than that of 24-day-old larvae.

Seawater carbonate chemistry, mortality and hatching rate, size and mass of Clupea harengus during experiments, 2011

Due to atmospheric accumulation of anthropogenic CO2 the partial pressure of carbon dioxide (pCO2) in surface seawater increases and the pH decreases. This process known as ocean acidification might have severe effects on marine organisms and ecosystems. The present study addresses the effect of ocean acidification on early developmental stages, the most sensitive stages in life history, of the Atlantic herring (Clupea harengus L.). Eggs of the Atlantic herring were fertilized and incubated in artificially acidified seawater (pCO2 1260, 1859, 2626, 2903, 4635 µatm) and a control treatment (pCO2 480 µatm) until the main hatch of herring larvae occurred. The development of the embryos was monitored daily and newly hatched larvae were sampled to analyze their morphometrics, and their condition by measuring the RNA/DNA ratios. Elevated pCO2 neither affected the embryogenesis nor the hatch rate. Furthermore the results showed no linear relationship betweenpCO2 and total length, dry weight, yolk sac area and otolith area of the newly hatched larvae. For pCO2 and RNA/DNA ratio, however, a significant negative linear relationship was found. The RNA concentration at hatching was reduced at higher pCO2 levels, which could lead to a decreased protein biosynthesis. The results indicate that an increased pCO2 can affect the metabolism of herring embryos negatively. Accordingly, further somatic growth of the larvae could be reduced. This can have consequences for the larval fish, since smaller and slow growing individuals have a lower survival potential due to lower feeding success and increased predation mortality. The regulatory mechanisms necessary to compensate for effects of hypercapnia could therefore lead to lower larval survival. Since the recruitment of fish seems to be determined during the early life stages, future research on the factors influencing these stages are of great importance in fisheries science.