Joachim Paul GrögerThünen Institute Bremerhaven / GEOMAR Kiel
Joachim Paul Gröger
Dipl., Dr. rer. nat., Dr. habil. (2x), Prof.
About
66
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Introduction
Joachim Paul Gröger is affiliated with the Thünen Institute of Sea Fisheries (Bremerhaven, Germany), GEOMAR (Kiel, Germany) and Rostock University (Rostock, Germany). He is based at GEOMAR, Düsternbrooker Weg 20, D-2410 Kiel, Germany. Joachim does research in Biostatistics, Ecology and Marine Biology and the develoment of autonomous stationary, portable and mobile UFOs (UFO = underwater fish observatory). Their current project is a national interdisciplinary innovation project named "UFOTriNet".
Publications
Publications (66)
Environmental enrichment aims for a deliberate increase in structural complexity in otherwise plain rearing units, helping to reduce aberrant traits and promote welfare of fish kept in captivity. Before putting enrichment protocols into practice, however, practitioners like hatchery managers need clear guidelines on enrichment measures and on the s...
The recovery of cormorant populations in Europe and North America caused controversial debates between resource users and nature conservationists; demands to control populations have been expressed in several occasions by the fishery sector. Yet, control strategies in most cases are rarely more than ad hoc efforts to appease fishermen and anglers;...
Atlantic cod (Gadus morhua) is an important recreational and commercial fisheries target species in the Northern hemisphere. Release rates are high in the recreational fishery due to regulatory and voluntary catch-and-release practice. Although post-release mortality of cod is relatively low, there is potential for further reductions. The most effe...
Northeast Atlantic marine ecosystems such as the Bay of Biscay, Celtic Sea, English Channel, Subpolar Gyre region, Icelandic waters and North Sea as well as the Mediterranean Sea show concomitant ‘regime shift’-like changes around the mid-1990s, which involved all biota of the pelagial: phytoplankton, zooplankton, pelagic fish assemblages, demersal...
The synchrony of pelagic fish population dynamics with climate variability may impose significant alterations in their distribution and biomass, as well as catch composition, with potential effects on ecosystems and fisheries. This work examines the effect of the Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) signals a...
The worldwide occurrence of complex climate-induced ecological shifts in marine systems is one of the major challenges in sustainable bio-resources management. The occurrence of ecological environment-driven shifts was studied in the Southern Caspian Sea using the “shiftogram” method on available fisheries-related (i.e. commercially important benth...
(English abstract below)
Kurzfassung
Optische Technologien und Verfahren sind sowohl in der limnischen als auch marinen Forschung Deutschlands über alle Bereiche und Skalen etabliert und entwickeln sich rasant weiter. Die Arbeitsgruppe „Aquatische Optische Technologien“ (AOT) will Forschern und Anwendern eine Plattform bieten, die Wissenstransfer...
Recent evolution experiments have revealed that marine phytoplankton may adapt to global change, for example to ocean warming or acidification. Long-term adaptation to novel environments is a dynamic process and phenotypic change can take place thousands of generations after exposure to novel conditions. Using the longest evolution experiment perfo...
Optische Technologien und Verfahren sind sowohl in der limnischen als auch marinen Forschung Deutschlands über alle Bereiche und Skalen etabliert und entwickeln sich rasant weiter. Die Arbeitsgruppe „Aquatische Optische Technologien“ (AOT) will Forschern und Anwendern eine Plattform bieten, die Wissenstransfer fördert, der nationalen Entwicklergeme...
Although ocean warming and acidification are recognized as two major anthropogenic perturbations of today’s oceans we know very little about how marine phytoplankton may respond via evolutionary change. We tested for adaptation to ocean warming in combination with ocean acidification in the globally important phytoplankton species Emiliania huxleyi...
Because of the high management relevance, commercial fish related aspects have often been central in marine ecosystem investigations. The iterative shiftogram method was applied to detect occurrence, type and timing of shifts in the single and multivariate time series linked to the spring spawning herring larvae in the Gulf of Riga (Baltic Sea). Al...
We examined factors affecting the fishing effort in the German brown shrimp (Crangon crangon) fishery, including shrimp and fuel price, catch per unit effort (cpue), number of days with strong wind, fishing port, and season. Time-series analysis (TS) using rational transfer functions (ARIMAX, an extension of autoregressive integrated moving average...
Climate forcing in complex ecosystems can have profound implications for ecosystem sustainability and may thus challenge a precautionary ecosystem management. Climatic influences documented to affect various ecological functions on a global scale, may themselves be observed on quantitative or qualitative scales including regime shifts in complex ma...
Fish larvae from the Celtic Sea were analysed to identify their distribution patterns, diversity and assemblage structure with regard to bathymetry and ocean warming. Samples were collected in April 2007 comprising larval stages of 60 fish species (3834 individuals) from 106 stations. Stations were divided into three major faunal zones, i.e. neriti...
Although oceanwarming and acidification are recognized as two major anthropogenic perturbations of today's oceanswe know very little about how marine phytoplankton may respond via evolutionary change.We tested for adaptation to ocean warming in combination with ocean acidification in the globally important phytoplankton species Emiliania huxleyi. T...
We have studied the annual variation in food intake of three sub-Antarctic ice fish species (Champsocephalus gunnari, Chaenocephalus aceratus, and Pseudochaenichthys georgianus) and three high-Antarctic ice fish species (Chionodraco rastrospinosus, Cryodraco antarcticus, and Chaenodraco wilsoni). Stomach content analyses were conducted during botto...
Critical transitions between alternative stable states have been shown to occur across an array of complex systems. While our ability to identify abrupt regime shifts in natural ecosystems has improved, detection of potential early-warning signals previous to such shifts is still very limited. Using real monitoring data of a key ecosystem component...
Temporal variance of Pseudocalanus acuspes (circles) and Acartia spp. (triangles) estimated by standard deviations (SD) and the first-order autocorrelation coefficient (AR(1)) of detrended time-series for a sliding window of 10 (A, D), 15 (B, E) and 20 (C, F) years. Vertical dashed bars mark the timing of the Central Baltic Sea regime shift in the...
Test results for recent trends and changes in trends over 3-year periods before the regime shift in 1988 using intersection–union tests. P-values from a χ2 goodness-of-fit test indicate whether the GAM fits satisfactory to the entire time-series. Significant negative (−) or positive (+) time trends in the rate of change (f′), as well acceleration (...
Map of the Baltic Sea and its location within Northern Europe. The central part of the Baltic Sea encompasses three deep (<70 m) basins important for marine biota, the Bornholm Basin (BB), the Gdansk Deep (GD) and the Gotland Basin (GB); largely corresponding to the International Council for the Exploration of the Sea (ICES) official sub-divisions...
Smoothed indicator time-series of Pseudocalanus acuspes and Acartia spp. with GAM df = 10 (A, B) and df = 20 (C, D) from 1960–1987. Bootstrapped confidence intervals are shown by grey lines. Acceleration in the rate of change (slope) in each year are shown by statistically significant second derivatives (f′′’), where black and white dots represent...
The degree of spatial correlation for Pseudocalanus acuspes (A) and Acartia spp. (B) estimated as the mean significance (p-value) of spatial correlation coefficients derived from a Moran’s I test across 6 (black), 8 (grey) and 10 (black) randomly assigned stations (after 1000 resamples). Vertical dashed bars mark the timing of the Central Baltic Se...
Hydroacoustic single fish detection and corresponding hydrographic measurements were used to study seasonal changes in vertical distribution of adult cod (Gadus morhua) in relation to ambient environmental conditions in the Bornholm Basin, central Baltic Sea. Sampling was conducted in April, June and August covering the years 2006–2009. Vertical di...
Regime shifts in ecosystems whose patterns and properties may be very complex and thus manifold have profound implications for sustainability. Detecting structural breaks in natural processes, however, turns out to be an ambitious task because the lack of well defined target values and reference periods renders application of standard statistical (...
Gröger, J. P., and Fogarty, M. J. 2011. Broad-scale climate influences on cod (Gadus morhua) recruitment on Georges Bank. – ICES Journal of Marine Science, 68: .
Climatic influences on Georges Bank cod recruitment were investigated using the North Atlantic Oscillation (NAO) as an index of atmospheric variability and the Atlantic Multidecadal Oscill...
Gröger, J. P., Kruse, G. H., and Rohlf, N. 2010. Slave to the rhythm: how large-scale climate cycles trigger herring (Clupea harengus) regeneration in the North Sea. – ICES Journal of Marine Science, 67: 454–465.
Understanding the causes of variability in the recruitment of marine fish stocks has been the “holy grail” of fisheries scientists for mo...
Payne, M. R., Hatfield, E. M. C., Dickey-Collas, M., Falkenhaug, T., Gallego, A., Gröger, J., Licandro, P., Llope, M., Munk, P., Röckmann, C., Schmidt, J. O., and Nash, R. D. M. 2009. Recruitment in a changing environment: the 2000s North Sea herring recruitment failure. – ICES Journal of Marine Science, 66: 272–277.
Environmentally induced change...
The extensive periodic vertical movements of up to 14 h and 209 m observed in this study for an individual goosefish, Lophius americanus, challenges previous assumptions about the benthic and highly sedentary behavior of the species as well as of other lophiids. Researchers should consider conducting similar data storage tagging studies with other...
The most abundant ice fish species observed in catches off the northern tip of the Antarctic Peninsula in the last 25–30years
has been the spiny ice fish Chaenodraco wilsoni Regan 1914. C. wilsoni has been exploited on a commercial scale from the late 1970s to the end of the 1980s off Joinville–D’Urville Islands (CCAMLR
Statistical Subarea 48.1) an...
Gröger, J. P., Rountree, R. A., Missong, M., and Rätz, H-J. 2007. A stock rebuilding algorithm featuring risk assessment and an optimization strategy of single or multispecies fisheries. – ICES Journal of Marine Science, 64: 1101–1115.
We present a simple but flexible stock-rebuilding algorithm model that features ideas of risk assessment, with all...
Information derived from archival tags (digital storage tags, DSTs) were used to backtrack the migration of 11 tagged Atlantic cod (Gadus morhua) during 2001 in Massachusetts Bay, the Gulf of Maine, and Georges Bank. The DST tags continuously recorded time, temperature and depth. To geolocate fish positions during its time at large, we first extrac...
Rätz, H-J., Bethke, E., Dörner, H., Beare, D., and Gröger, J. 2007. Sustainable management of mixed demersal fisheries in the North Sea through fleet-based management—a proposal from a biological perspective. – ICES Journal of Marine Science, 64: 652–660.
Cod, haddock, whiting, saithe, plaice, sole, and Norway lobster are main target species for th...
Our study uniquely analyzes the population structure (stock sizes N in numbers, biomass B, recruitment R, spawning stock biomass SSB, yield-per-recruit Y/R, catch-to-biomass ratios Y/B) and the influence of natural (North Atlantic Oscillation NAO, regional environmental variables) and anthropogenic (fishing mortality F) forces on the population dyn...
Rountree, R.A., J.P. Groeger, and D. Martins. 2006b. Migration and vertical movements of a tagged Atlantic goosefish on Georges Bank. Presented at the 2006 Joint Meeting of Ichthyologists and Herpetologists, July 12-17, 2006, New Orleans, La.
Long-term macrobenthos data from Kiel Bight in the Western Baltic collected between 1968 and 2000 have been correlated with the winter NAO index (North Atlantic Oscillation Index) and other environmental data such as temperature, salinity and oxygen content in the bottom water in order to detect systematic patterns related to so far unexplained abi...
Depth (pressure) and temperature measurements recorded on a data storage tag were
examined from a single goosefish, Lophius americanus, tagged on Georges Bank on 9 December
2003 and recaptured 192 days and 113 km away off Cape Cod, Massachusetts on June 18, 2004.
The monkfish exhibited a strong pattern of periodic vertical movements ranging from 4...
The High-Resolution Trawl Survey project was established as a collaboration between
the New Bedford Massachusetts commercial fishing industry and the School for Marine Science
and Technology at the University of Massachusetts Dartmouth. A major incentive for the
project was to recognize the desire of the fishing community to participate more direct...
We collaborated with the New Bedford trawl fleet to collect catch from the Georges Bank groundfish fishery between November 2000 and August 2004. A major incentive for the project was to recognize the desire of the commercial fishing community to participate more directly in the management of the resource. Catch data were recorded from 7,911 trawl...
Time series on Crangon crangon densities in the German Wadden Sea show a considerable degree of interannual variability, for the entire region in spring and in autumn as well as for three subareas, North Frisia, East Frisia and Elbe estuary. Across the entire survey area C. crangon density was inversely related to water depth. In autumn after the r...
Fish landings in the Baltic Sea from 1970 to 2000 were used as a proxy for fish biomass to explore variability of total fish biomass. Total demersal (total D) and total pelagic (total P) landings proved relatively invariant over time compared with most of their component species. This was explained in terms of the energy limitation imposed on the e...
Length distributions of fish were analysed based on data from the German annual (November/December) bottom trawl surveys in the Mecklenburg Bight and Arkona Basin [ICES Subdivisions (SD) 22 and 24, respectively] of the southwest Baltic Sea, covering the period from 1991 to 2000. The length spectra for all fish species, and those for demersal and pe...
Biometric issues arise concerning the accuracy and precision of age determinations, for instance in herring otolith readings, due to the influence of random and systematic factors. Biostatistical methods are employed to propose various biometric solutions with regard to the number of otoliths to be read, on the basis of the precision required. The...
Biometric issues arise concerning the accuracy and precision of age determinations, for instance in herring otolith readings, due to the influence of random and systematic factors. Biostatistical methods are employed to propose various biometric solutions with regard to the number of otoliths to be read, on the basis of the precision required. The...
A basic stock assessment problem is the mixing and separation of herring populations in their specific areas. Within the transition zone between the North and the Baltic seas (Skagerrak, Kattegat, The Sound) a mixing of two herring populations (Clupea harengus L.) temporarily takes place. One major component stems from the Baltic Sea (spring spawne...
The objective was to find a length–growth model to help differentiate between herring stocks (Clupea harengus l.) when their length–growth shows systematically different patterns. The most essential model restriction was that it should react robustly against variations in the underlying age range which varies not only over time but also between the...
The ICES International Herring Larvae Survey Program (IHLS), regularly carried out since 1972 in the North Sea and adjacent areas, provides an abundance index to be utilised by the ICES Herring Assessment Working Group. This is one of three indices for assessing the state of the herring stock components in the North Sea by means of VPA (Virtual Pop...
A detailed analysis of beak length to body size and mass measurements was carried out for the glacial squid Psychroteuthis glacialis, which is an endemic cephalopod species in the Southern Ocean. Beak lengths (lower rostral length) were measured from 211
specimens which had been sampled in the Atlantic sector of the Southern Ocean. The basic idea w...
Quite frequently scientists do not publish the original data but only their results or parts of it leading to incomplete literature information. In order to compare reduced morphometric literature information with morphometric data derived from own measurements, we have adopted and modified an econometric method for the purpose of stock discriminat...
Two stocks of herring (Clupea harengus L.) mix temporarily in the transition area between Baltic and North Seas. A new model for their separation is proposed using a weighted logistic regression approach. This model is based on vertebrae counts and parameterised using samples of the German hydroacoustic survey in the eastern North Sea and in the so...
Age reading by use of otoliths or any other hard structure is one of the basic practical elements in fish population dynamics. In order to manage the interpersonal standardization and correction problem of age readings, respectively, from a statistical point of view calibration techniques will be introduced here. The current paper does not only pre...
Age reading by use of otoliths or any other hard structure is one of the basic practical elements in fish population dynamics. In order to manage the interpersonal standardization and correction problem of age readings, respectively, from a statistical point of view calibration techniques will be introduced here. The current paper does not only pre...
The Elephant Island region (Antarctic Peninsula) was selected as a long-term monitoring site to describe the interannual
variability of important krill stock parameters. The analysis reviewed and updated krill density and proportional recruitment
indices. Krill absolute recruitment and biomass from net sampling surveys are introduced as additional...
Blue mussels Mytilus edulis L. and eelgrass Zostera marina L. commonly co-occur in mixed stands at sheltered sites of the Western Baltic. The effects of mussels on density, vegetative propagation and growth of eelgrass were tested experimentally. Mussels were either added to Z. marina patches or removed from existing Zostera/Mytilus associations. W...
The diet composition and feeding intensity of mackerel icefish Champsocephalus gunnari around Shag Rocks and the mainland of South Georgia was analyzed from ca 8700 stomachs collected in January/February 1985, January/February 1991 and January 1992. Main prey items were krill Euphausia superba, the amphipod hyperiid Themisto gaudichaudii, mysids (p...
Projects
Projects (2)
The aim of the present project is to develop a trilateral test network consisting of a mobile and a portable underwater fish observatory (UFO), to link both with an existing pre-prototype UFO, to standardize the automatic pattern recognition for all three components and to optimize them so that species, size and weight classification can be achieved with a high statistical certainty (at least 95%). It is a highly interdisciplinary, complex topic that must include biological, physical-oceanographic, geographic as well as technical, logistical, political and legal conditions. The resulting data (acoustics, stereo optics, environmental sensors) should be fed into an integrated, newly to be built data and information system with online access. In this way, an automated, cost-effective and non-invasive alternative to ship-based monitoring of fish stocks will be developed and tested in Kiel Bight as a contribution to a reformed, evidence-based fisheries policy. Similar to the existing stationary UFO system, the mobile and the portable underwater fish observatories will also combine modern acoustic and optical methods for monitoring fish stocks being provided as a coupled hybrid system (coupling of near field (optics) and far field (acoustics)). The coupled system tests in Kiel Bight ensure low logistics costs, as they are performed close to the coast. Additional research vessel sampling campaigns will provide comparative information for data calibration, data blending, and data conversion, while at the same time providing an important contribution for an improved understanding of the processes helping to optimize hardware design and pattern recognition algorithms for the trilateral UFO network.
This project is financially supported by the Federal Ministry of Food and Agriculture (BMEL), grant number 2819111618.
