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Axel Temming - One of the best experts on this subject based on the ideXlab platform.
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environmental effects on Sprat Sprattus Sprattus physiology and growth at the distribution frontier a bioenergetic modelling approach
Ecological Modelling, 2015Co-Authors: Christina Frisk, Axel Temming, Jens-peter Herrmann, Ken Haste Andersen, Kathrine Skak Madsen, Gerd KrausAbstract:Abstract Sprat, Sprattus Sprattus , is a small pelagic fish species with a wide distribution along the European continental shelf, the Mediterranean Sea, the Black Sea and the Baltic Sea. The Baltic Sea is the coldest area of the species distribution range. Even here, Sprat is still numerous and holds a key role in the ecosystem. However, the population is sensitive to small changes in environmental conditions. In this paper, we set up a bioenergetic model of Baltic Sprat and evaluate how variability and seasonal changes in the physical environment affects the physiology and growth of individual Sprat. The model is dynamic and seasonally resolved. It is parameterised based on Sprat from the Bornholm Basin. Our model results suggest that the optimal temperature for Sprat growth is 17.5 °C, which is only observed in the Central Baltic Sea in the top water layer during a short period in summer. During 4½ winter months individual Sprat do not grow and utilize stored energy from the previous growth season. We analysed the maximum attainable individual body size as a function of temperature. The model predicted reduced maximum body sizes with increasing temperature. The model can be used for studying climate change scenarios on individual growth, egg production and condition of Baltic Sprat.
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vertically resolved prey selectivity and competition of baltic herring clupea harengus and Sprat Sprattus Sprattus
Marine Ecology Progress Series, 2013Co-Authors: Matthias Bernreuther, Jörn Schmidt, Daniel Stepputtis, Axel TemmingAbstract:Prey selectivity of Baltic herring Clupea harengus and Sprat Sprattus Sprattus was studied in the Bornholm Basin, Baltic Sea, in June 2001. A total of 165 Sprat stomachs (10 to 15 cm total length, TL) and 214 herring stomachs (12 to 30 cm TL) were analysed. The diel vertical distribution of zooplankton prey was analysed by multi-net samples; clupeid distributions were estimated by hydroacoustic measurements. These measurements enabled us to describe the diel feeding rhythm and to estimate vertically resolved selectivity indices for the 2 most important zoo-planktivores in the Baltic Sea. Diet composition of herring and Sprat were similar (mainly copepods and cladocerans), resulting in strong competition. Possibly to reduce this competition, both species were partly specializing on certain prey species (Sprat: Podon spp.; herring: Evadne nordmanni and Temora longicornis) and copepodite stages (Sprat: adult [C6] males of Pseudocalanus acuspes; herring: C6 females of P. acuspes). Sprat and, to some extent, herring exhibited a marked shift in prey preference between day and night. Sprat mainly selected T. longicornis during the day and Podon spp. during the night, while herring mainly selected T. longicornis during the day and E. nordmanni during parts of the night. A comparison of the field stomach contents with the estimated gastric evacuation predicted by parameters based on laboratory experiments indicated that Sprat fed during the night, while herring did not or only to a minor extent. Comparison of our zooplankton sampling scheme with commonly used sampling designs revealed that investigations which consider both time and stage are needed to fully understand the feeding selectivity dynamics of herring and Sprat in the Baltic Sea. However, the objective of a selectivity study should determine the most appropriate zooplankton sampling scheme.
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dietary overlap between the potential competitors herring Sprat and anchovy in the north sea
Marine Ecology Progress Series, 2012Co-Authors: K Raab, C Boeree, Axel Temming, Leopold A. J. Nagelkerke, Adriaan D. Rijnsdorp, Mark DickeycollasAbstract:European anchovy Engraulis encrasicolus increased its abundance and distribution in the North Sea during the mid-1990s and may consume similar zooplankton to and/or compete with other occupants of the North Sea like herring Clupea harengus and Sprat Sprattus Sprattus. The diets of adult anchovy, Sprat and juvenile herring of comparable sizes, sampled close in time and space, were compared to understand how the 3 species prey on zooplankton and establish whether their diets overlap or not. Anchovy was found to be more generalist, consuming a higher diversity of prey items. Herring was more specialized, with low diversity of food items. Sprat was intermediate between anchovy and herring. The dietary overlap between anchovy and Sprat was highest, followed by herring and Sprat before anchovy and herring. The mean weight of stomach contents did not differ between species. We conclude that of the 3 species, anchovy is likely to be the least affected by changing plankton communities.
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Investigating the selective survival of summer-over spring-born Sprat, Sprattus Sprattus, in the Baltic Sea
Fisheries Research, 2008Co-Authors: Hannes Baumann, Rudi Voss, Hans-harald Hinrichsen, Volker Mohrholz, Joern O. Schmidt, Axel TemmingAbstract:To better understand recruitment variability in small pelagic fish like Sprat, it is important to know when during the extended spawning season the successful recruits are predominantly produced and which environmental factors determine potential survival windows. Here, we inferred the temporal origin of 2-year classes (2002–2003) of western and central Baltic Sprat by means of otolith microstructure analysis, and found that in both years recruits mainly originated from the summer months June and July. In both years, this period coincided with temperature conditions in the surface layer of >12 °C and peak seasonal abundance of the largest copepod stages of Acartia spp., the major prey item of Sprat larvae. The peaks in seasonal Sprat egg abundance, however, occurred in April 2002 and March 2003 and therefore about 1–2 months earlier than the long-term mean spawning peak of Sprat in this area (end of May/beginning of June). We hypothesize that increased temperatures in the bottom layer of the Baltic, where the pre-spawning Sprat stock concentrates during winter months, potentially caused this shift in Sprat spawning patterns, although early spring temperatures and feeding conditions in upper water layers were still unfavourable for larval survival. Sprat recruitment, however, was comparatively strong in both 2002 and 2003, suggesting that summer born individuals had high enough survival rates to compensate for the spawning shift, possibly due to high summer temperatures, limited dispersion, and low predation mortalities by Baltic cod as the major predator of Sprat. Recruits were on average younger in 2003 than 2002, yet length distributions in October were almost identical, likely because a period of substantially higher temperatures in July/August 2003 promoted faster initial (larval) growth of survivors. Given the strength of the 2003 year class, in spite of lower overall prey concentrations in 2003 than 2002 in the study area, our findings appear to emphasise the paramount importance of summer temperatures as the recruitment determinant in Baltic Sprat
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Depth-dependent nutritional condition of Sprat Sprattus Sprattus larvae in the central Bornholm Basin, Baltic Sea
Marine Ecology Progress Series, 2007Co-Authors: Andreas Dänhardt, Myron A. Peck, Catriona Clemmesen, Axel TemmingAbstract:Bimodal depth distribution patterns observed for Sprat Sprattus Sprattus larvae in previous field studies conducted in the deep basins of the Baltic Sea have led researchers to hypothesise that larval Sprat condition was depth-dependent. We examined this hypothesis by measuring morphological, biochemical and otolith-based proxies for nutritional condition in Sprat larvae collected in discrete 5 m depth intervals from the surface to the bottom in the central Bornholm Basin. Similar to earlier studies, larval Sprat were most abundant in 2 depth strata (0 to 10 and 65 to 75 m). Their nutritional condition in surface and deep waters was not uniformly expressed by the different indices. For example, Sprat larvae from 0 to 10 m could not be distinguished from conspecifics caught at 65 to 75 m by a long-latency condition proxy (otolith-based growth rates). Similarly, a medium-latency proxy (RNA:DNA) did not suggest differences in condition between the depths. However, short-latency proxies (protein:standard length and DNA:dry weight) supported the depth-dependent condition hypothesis. The lack of correspondence and pitfalls associated with the use and interpretation of multiple condition indices (e.g. the influences of temperature and body size) are discussed and recommendations to strengthen these various metrics are provided.
Friedrich W Koster - One of the best experts on this subject based on the ideXlab platform.
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recruitment variability in baltic sea Sprat Sprattus Sprattus is tightly coupled to temperature and transport patterns affecting the larval and early juvenile stages
Canadian Journal of Fisheries and Aquatic Sciences, 2006Co-Authors: Hannes Baumann, Friedrich W Koster, Christian Mollmann, Hans-harald Hinrichsen, Arne M Malzahn, Axel TemmingAbstract:Recruitment patterns of Baltic Sea Sprat (Sprattus Sprattus) were correlated to time series of (i) month- and depth-specific temperature conditions and (ii) larval drift patterns inferred from long-term Lagrangian particle simula- tions. From the latter, we derived an index that likely reflected the variable degree of annual larval transport from the central, deep spawning basins to the shallow coastal areas of the Baltic Sea. The drift index was significantly (P < 0.001) correlated to Sprat recruitment success and explained, together with Sprat spawning stock biomass, 82% of the overall variability between 1979 and 2003. Years of strong larval displacement towards southern and eastern Baltic coasts corresponded to relative recruitment failure, while years of retention within the deep basins were associated with relative recruitment success. The strongest correlation between temperature and recruitment occurred during August in surface waters, explaining 73% of the overall variability. Together, the two approaches advocate that new year classes of Baltic Sprat are predominantly composed of individuals born late in the season and are determined in strength mainly by processes acting during the late larval and early juvenile stages. However, prior to be included in recruit- ment predictions, the biological mechanisms underlying these strong correlations may need to be better resolved.
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climate zooplankton and pelagic fish growth in the central baltic sea
Ices Journal of Marine Science, 2005Co-Authors: Christian Mollmann, Marina Fetter, Georgs Kornilovs, Friedrich W KosterAbstract:Oceanographic conditions in the brackish central Baltic Sea are strongly linked to atmospheric forcing and the unusual period of persistently strong westerlies that, since the late 1980s, have resulted in an increase in average water temperatures and decreasing salinity. These changes in temperature and salinity resulted in a change in the dominance of the mesozooplankton community from Pseudocalanus sp. to Temora longicornis and Acartia spp. Similar to the copepod community, the central Baltic fish community shifted from cod (Gadus morhua), dominant during the 1980s, to Sprat (Sprattus Sprattus), dominant during the 1990s. Further, the commercially important pelagic fish species herring (Clupea harengus) and Sprat exhibited reductions in growth. Using Principal Component and Correlation Analyses we investigated the temporal variability in the importance of the food supply as well as competition on condition of central Baltic pelagic fish species. Our results indicate that herring condition results from a combined effect of changes in the food environment and increased competition with Sprat, while Sprat condition appeared to be primarily determined by intra-specific competition.
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feeding ecology of central baltic sea herring and Sprat
Journal of Fish Biology, 2004Co-Authors: Christian Mollmann, Georgs Kornilovs, M Fetter, Friedrich W KosterAbstract:A unique dataset of stomach contents sampled between 1977 and 1999 in the central Baltic Sea was used to perform a comprehensive study of the feeding ecology of Central Baltic herring Clupea harengus and Sprat Sprattus Sprattus. Both fish species were mainly preying upon calanoid copepods with Pseudocalanus sp. dominating the diet of herring, whereas Sprat generally preferred Temora longicornis. Sprat preyed upon older copepodite stages, indicating size-selective particulate feeding, whereas herring additionally fed on smaller copepodite stages, indicating occasional low food supply inducing filter-feeding. Additional food sources other than copepods were mysids in winter and autumn for medium to large herring, as well as cladocerans for Sprat in spring and summer, determined by the seasonal occurrence of these plankton species. Seasonally the highest feeding activity of both fishes species occurred in spring and summer, the main reproductive periods of calanoid copepods. The most important food item for both predators in spring was Pseudocalanus sp. In summer Sprat switched to T. longicornis and Acartia spp. Since the late 1970s, the total stomach fullness decreased and the fraction of empty stomachs increased. In parallel the amount of Pseudocalanus sp. in the diets of both fish species decreased. Further, a considerable dietary overlap between both species in spring indicated considerable competition for food resources, especially due to an enlarged Sprat stock. The results of this study support the hypothesis that growth reductions observed in Baltic herring and Sprat are due to combination of a change in food availability and an increase in density-dependent competition.
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estimating baltic Sprat Sprattus Sprattus balticus s population sizes from egg production
Fisheries Research, 2004Co-Authors: Gerd Kraus, Friedrich W KosterAbstract:The Sprat (Sprattus Sprattus balticus S.) population size in the Bornholm Basin, one of the major spawning areas of the species in the Baltic Sea, was estimated with the daily egg production method. Egg abundance, stock structure, sexual and gonadal maturation, spawning frequency and the batch fecundity of Sprat throughout the Sprat spawning season were simultaneously investigated to obtain an estimate of the population size at spawning time. The results confirmed the population estimate from a hydroacoustic survey, but contrasted spatially down-scaled results from an area dis-aggregated stock assessment model applying fisheries statistics. Conflicting results from both latter methods have previously hampered quantitative studies on recruitment processes of Sprat and cod, for example the estimation of predation pressure on cod eggs by Sprat. The egg production method did not allow an estimation of the population size of Sprat in the entire assessment area larger than the Bornholm Basin, i.e. ICES sub-division 25. This failure is caused by Sprat spawning activity outside the Bornholm Basin, not covered by the standard egg surveys and has consequences for the general applicability of available egg abundance time series to retrospectively estimate Sprat stock development.
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fish production and climate Sprat in the baltic sea
Ecology, 2004Co-Authors: Brian R Mackenzie, Friedrich W KosterAbstract:Processes controlling the production of new fish (recruitment) are poorly understood and therefore challenge population ecologists and resource managers. Sprat in the Baltic Sea is no exception: recruitment varies widely between years and is virtually independent of the biomass of mature Sprat. Sprat is a key prey and predator species in the Baltic ecosystem and is commercially exploited (1.86 × 108 kg/yr since 1974). The population and fishery must therefore be managed sustainably and if necessary accommodate environmental effects on population dynamics. We demonstrate using 45 years of data that recruitment depends on temperature conditions during the months when Sprat gonads, eggs, and larvae are developing. We also show that recruitment can be predicted before adults spawn (and fully 15 months earlier than using present technology) by using linkages between recruitment, large-scale climate variability (North Atlantic Oscillation), Baltic Sea ice coverage, and water temperature. These relationships increase our understanding of Sprat population dynamics and enable a desirable integration of fisheries ecology and management with climatology and oceanography.
Michele Casini - One of the best experts on this subject based on the ideXlab platform.
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Linking consumer physiological status to food-web structure and prey food value in the Baltic Sea
Ambio, 2020Co-Authors: Agnes M. L. Karlson, Michele Casini, Elena Gorokhova, Anna Gårdmark, Zeynep Pekcan-hekim, Jan Albertsson, Brita Sundelin, Olle Karlsson, Lena BergströmAbstract:Declining physiological status in marine top consumers has been observed worldwide. We investigate changes in the physiological status and population/community traits of six consumer species/groups in the Baltic Sea (1993–2014), spanning four trophic levels and using metrics currently operational or proposed as indicators of food-web status. We ask whether the physiological status of consumers can be explained by food-web structure and prey food value. This was tested using partial least square regressions with status metrics for gray seal, cod, herring, Sprat and the benthic predatory isopod Saduria as response variables, and abundance and food value of their prey, abundance of competitors and predators as predictors. We find evidence that the physiological status of cod, herring and Sprat is influenced by competition, predation, and prey availability; herring and Sprat status also by prey size. Our study highlights the need for management approaches that account for species interactions across multiple trophic levels.
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growth and maturity of Sprat Sprattus Sprattus in the kattegat and skagerrak eastern north sea
Aquatic Living Resources, 2015Co-Authors: Francesca Vitale, Felix Mittermayer, Birgitta Krischansson, Marianne Johansson, Michele CasiniAbstract:Information on fish biology, as growth and reproduction, is an essential first step for a sound assessment and management of a fishery resource. Here we analyzed the annual cycle of body condition factor (K ), gonadosomatic index (GSI ) and maturity of Sprat from the Skagerrak and Kattegat as well as from the Skagerrak inner fjords (Uddevalla fjords). The results show an inverse yearly pattern for K and GSI in both areas, K being the highest in autumn and lowest in spring, while the GSI index was highest in spring and lowest in autumn. The annual highest proportion of spawning fish was recorded from May to July, indicating the late spring and early summer as the main spawning period for Sprat in these areas. Male Sprat reached maturity at a higher size in the Uddevalla fjords compared to Skagerrak and Kattegat, while negligible differences were shown by females. The K , GSI and size-at-age were the lowest in the Uddevalla fjords, while K and GSI were the highest in the Skagerrak, potentially related to the different environmental conditions encountered in the different areas. All in all the present results furnish important information about the biology of the Sprat in the area that is highly relevant in stock assessment and management. The potentiality for the Sprat inhabiting the Uddevalla fjords to be a different sub-population should be addressed through further investigations.
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density dependence in space and time opposite synchronous variations in population distribution and body condition in the baltic sea Sprat Sprattus Sprattus over three decades
PLOS ONE, 2014Co-Authors: Michele Casini, Valerio Bartolino, Tristan Rouyer, Niklas Larson, Wlodzimierz GrygielAbstract:Spatio-temporal density-dependent processes are crucial regulatory factors for natural populations. However, there is a lack of studies addressing spatial density-dependence in fish growth. A previous investigation has suggested spatio-temporal density-dependence in body condition of Baltic Sprat. Here, we used different techniques, such as centre of gravity, distance, and homogeneity indices, to better characterize the spatial and temporal variations in Sprat density and body condition in the Baltic Proper. Our results evidenced a negative spatio-temporal co-variation between the centres of gravity of density and maximum condition. In the 1980s-early 1990s both centres were located in the middle of the Baltic Proper. From the mid 1990s the centres progressively separated in space, as the Sprat population moved towards the north-eastern Baltic Proper, and the centre of maximum condition towards the south-western areas. Moreover, at low abundances, Sprat density and condition were homogeneously distributed in space, whereas at high abundances both density and condition showed pronounced geographical gradients. The ecological processes potentially explaining the observed patterns were discussed in the light of the Ideal Free Distribution theory. We provide evidence that the shift in the spatial distribution of cod, the main predator of Sprat, has been the main factor triggering the overall spatial changes in Sprat density, and thus condition, during the past thirty years. The spatial indices shown here, synthesizing the spatio-temporal patterns of fish distribution, can support the implementation of the EU Marine Strategy Framework Directive.
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the thiamine deficiency syndrome m74 a reproductive disorder of atlantic salmon salmo salar feeding in the baltic sea is related to the fat and thiamine content of prey fish
Ices Journal of Marine Science, 2012Co-Authors: Marja Keinänen, Michele Casini, Timo Myllylä, Jukka Pönni, Annika Uddstrom, Jaakko Mikkonen, Pekka J. VuorinenAbstract:This study clarifies how the diet of Baltic salmon leads to thiamine deficiency in eggs, and consequently to M74 mortality of yolk-sac fry. The main prey species, Sprat (Sprattus Sprattus) and herring (Clupea harengus membras), and their biomass in the Baltic Proper (BPr) and the Bothnian Sea, the two feeding grounds of salmon originating from the northern Gulf of Bothnia rivers, are compared. The thiamine concentration of both prey species is lowest in the youngest age groups. Because average fat content and energy density are greater in Sprat than in herring, and greatest in youngest Sprat, the supply of thiamine per unit energy is least in a diet containing many young Sprat. Also, the greater is the supply of thiamine and fat from Sprat in the southern BPr in the preceding year, the lower the concentration of thiamine in salmon eggs. Thiamine deficiency in eggs results from an unbalanced diet abundant in fatty prey fish, such as young Sprat, from which the supply of thiamine is insufficient in proportion to the supply of energy and unsaturated fatty acids for salmon, which must undergo a long prespawning fasting period.
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spatial and temporal density dependence regulates the condition of central baltic sea clupeids compelling evidence using an extensive international acoustic survey
Population Ecology, 2011Co-Authors: Michele Casini, Georgs Kornilovs, Christian Mollmann, Massimiliano Cardinale, Wlodzimierz Grygiel, Patrik Jonsson, Tiit Raid, Juha Flinkman, Valeriy FeldmanAbstract:For the first time an international acoustic survey dataset covering three decades was used to investigate the factors shaping the spatial and temporal patterns in the condition of Sprat and herring in the Baltic Proper. Generalized additive models showed that the spatial and temporal fluctuations in Sprat density have been the main drivers of the spatio-temporal changes of both Sprat and herring condition, evidencing intra- and inter-specific density dependence mediated by the size and distribution of the Sprat population. Salinity was also an important predictor of herring condition, whereas temperature explained only a minor part of Sprat model deviance. Herring density was an additional albeit weak significant predictor for herring condition, evidencing also intra-specific density dependence within the herring population. For both species, condition was high and similar in all areas of the Baltic Proper until the early 1990s, coincident with low Sprat densities. Afterwards, a drop in condition occurred and a clear south–north pattern emerged. The drop in condition after the early 1990s was stronger in the northern areas, where Sprat population increased the most. We suggest that the increase in Sprat density in the northern areas, and the consequent spatial differentiation in clupeid condition, have been triggered by the almost total disappearance of the predator cod from the northern Baltic Proper. This study provides a step forward in understanding clupeid condition in the Baltic Sea, presenting evidence that density-dependent mechanisms also operate at the spatial scale within stock units. This stresses the importance of spatio-temporal considerations in the management of exploited fish.
Rüdiger Voss - One of the best experts on this subject based on the ideXlab platform.
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the spatial dimension of climate driven temperature change in the baltic sea and its implication for cod and Sprat early life stage survival
Journal of Marine Systems, 2012Co-Authors: Rüdiger Voss, Christoph Petereit, Jörn Schmidt, Andreas Lehmann, Andrei Makarchouk, Hans-harald HinrichsenAbstract:Abstract Throughout the last decades there has been a world-wide, general warming trend. In this study, we use the example of the Baltic Sea to resolve the overall estimated temperature trend into smaller, meso-scale spatial units. Afterwards, we investigate the spatially resolved potential impact of the temperature trend on larval survival for two important fish species, cod and Sprat. We used two different sets of hydrographic data: (i) long-term temporally and depth-resolved data measured in situ originating from one geographic position and (ii) long-term horizontally resolved data, originating from a circulation model. In contrast to basin-wide integrated results, our modelling approach revealed different results related to smaller spatial scales. In shallow and coastal areas non-significant long-term temperature trends were observed. In some cases even decreasing temperature trends were found. Average distribution maps (1973–2010) of cod and Sprat eggs and larvae confirmed the higher importance of central, deep basins as nursery grounds. Applying the temperature trends when calculating cod larval window of opportunity values, resulted in decreased durations of 1–3 days (~ 3–13%) in most areas. Sprat larval window of opportunity values mainly increased up to 4 days (~ 45%), indicating a potential reproduction advantage of Sprat over cod under anticipated future temperature increase.
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survival probability of larval Sprat in response to decadal changes in diel vertical migration behavior and prey abundance in the baltic sea
Limnology and Oceanography, 2010Co-Authors: Hans-harald Hinrichsen, Myron A. Peck, Jörn Schmidt, Bastian Huwer, Rüdiger VossAbstract:We employed a coupled three-dimensional biophysical model to explore long-term inter- and intra-annual variability in the survival of Sprat larvae in the Bornholm Basin, a major Sprat spawning area in the Baltic Sea. Model scenarios incorporated observed decadal changes in larval diel vertical distribution and climate-driven abiotic and biotic environmental factors including variability in the abundance of different, key prey species (calanoid copepods) as well as seasonal changes, long-term trends, and spatial differences in water temperature. Climate forcing affected Baltic Sprat larval survival both directly (via changes in temperature) and indirectly (via changes in prey populations). By incorporating observed changes in larval diel vertical migration, decadal changes in modeled and observed survival of Baltic Sprat agreed well. Higher larval survival (spawning stock biomass) was predicted in the 1990s compared to the 1980s. After changing their foraging strategy by shifting from mid-depth, low prey environment to near-surface waters, first-feeding larvae encountered much higher rates of prey encounter and almost optimal feeding conditions and had a much higher growth potential. Consequently, larvae were predicted to experience optimal conditions to ensure higher survival throughout the later larval and early juvenile stages. However, this behavioral shift also increased the susceptibility of larvae to unfavorable winddriven surface currents, contributing to the marked increase in interannual variability in recruitment observed during the past decade.
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environmental factors influencing larval Sprat Sprattus Sprattus feeding during spawning time in the baltic sea
Fisheries Oceanography, 2008Co-Authors: Rüdiger Voss, Hans-harald Hinrichsen, Miriam Dickmann, Jens FloeterAbstract:The management of Baltic Sprat is challenged by highly variable recruitment success and hence large stock fluctuations. Recent studies have identified the larval and early juvenile life stages to be critical for the survival rate of a Sprat year class. Although prey abundance was found to be linked to larval survival success, an analysis identifying the functional relationship and relative importance of other environmental factors is still missing. Sprat larval feeding was investigated in 2002 during three cruises, covering the main spawning time in the Bornholm Basin, Baltic Sea. The aim of the study was to identify the key environmental factors determining the feeding success of larval Sprat taking their potential interactions explicitly into account. An extension of generalized additive models (GAMs) was adopted that allows the inclusion of interaction terms in a non-parametric regression model. The final model of Sprat larval feeding success explained ∼80% of the variance in the data and was based on the following environmental factors: bottom depth, cubed wind speed as proxy for small-scale turbulence rates, degree of cloudiness as proxy for light conditions and prey density in combination with a feeding period–cloudiness interaction term. Our study demonstrates that the feeding success of Sprat larvae in the Baltic Sea is controlled by a number of simultaneously acting key environmental factors.
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feeding ecology of central baltic Sprat Sprattus Sprattus larvae in relation to zooplankton dynamics implications for survival
Marine Ecology Progress Series, 2007Co-Authors: M Dickmann, Christian Mollmann, Rüdiger VossAbstract:We investigated the larval feeding ecology of Sprat Sprattus Sprattus L., an important commercial fish species in the Central Baltic Sea. We collected seasonally resolved larval abundance and gut content as well as zooplankton data, with the goal of identifying mechanisms leading to variability in larval survival. Our results show Sprat larvae feed progressively on larger food items as they grow during the season depending on their size and the composition of the available prey. We found first-feeding larvae early in the spawning season to prey exclusively upon microplankton. Small larvae fed mainly upon nauplii of the copepods Acartia spp., Temora longicornis and Centropages hamatus (ca. 65%), whereas larger larvae consumed up to 80% Acartia spp. copepodites and adults, as well as cladocerans. Trends in Sprat larval diets were to a large degree explainable by selective feeding. Feeding success and gut fullness increased linearly with larval size. Trophic niche breadth increased linearly until larvae reached a predator size of 16 mm, after which it decreased. We explain the latter decline by a restricted size spectrum of prey available to larger Sprat larvae, which points towards the importance of considering the structure of the zooplankton community when evaluating the predator size to niche breadth relationship. Our results suggest first-feeding Baltic Sprat larvae to be always food-limited, while larger larvae are not. We hypothesize medium-sized Sprat larvae to be the life stage that has the potential to cause most of the interannual variability in Sprat larval survival, which is dependent on a match between larval production and the state of the plankton cycle.
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Vertical distribution of Baltic Sprat larvae: changes in patterns of diel migration?
ICES Journal of Marine Science, 2007Co-Authors: Rüdiger Voss, Jörn Schmidt, Dietrich SchnackAbstract:Ontogenetic and diurnal vertical migration patterns of Baltic Sprat larvae were investigated for the periods 1989–1990 and 1998–2002. Comparison of the results led to the hypothesis that the diel vertical migration behaviour of Sprat larvae >10 mm has changed. In 1989 and 1990, Sprat larvae migrated to the surface at night, whereas they stayed 30–50 m deep by day. From 1998 to 2002, Sprat larvae showed no signs of diel vertical migration, remaining in warmer, near-surface water by day and night. This behavioural change coincided with a more general change in the Baltic ecosystem, i.e. an increase in near-surface temperature and a general increase in abundance of the major prey organism (Acartia spp.) of Baltic Sprat larvae, with more pronounced aggregation in surface waters.
Christian Mollmann - One of the best experts on this subject based on the ideXlab platform.
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spatial and temporal density dependence regulates the condition of central baltic sea clupeids compelling evidence using an extensive international acoustic survey
Population Ecology, 2011Co-Authors: Michele Casini, Georgs Kornilovs, Christian Mollmann, Massimiliano Cardinale, Wlodzimierz Grygiel, Patrik Jonsson, Tiit Raid, Juha Flinkman, Valeriy FeldmanAbstract:For the first time an international acoustic survey dataset covering three decades was used to investigate the factors shaping the spatial and temporal patterns in the condition of Sprat and herring in the Baltic Proper. Generalized additive models showed that the spatial and temporal fluctuations in Sprat density have been the main drivers of the spatio-temporal changes of both Sprat and herring condition, evidencing intra- and inter-specific density dependence mediated by the size and distribution of the Sprat population. Salinity was also an important predictor of herring condition, whereas temperature explained only a minor part of Sprat model deviance. Herring density was an additional albeit weak significant predictor for herring condition, evidencing also intra-specific density dependence within the herring population. For both species, condition was high and similar in all areas of the Baltic Proper until the early 1990s, coincident with low Sprat densities. Afterwards, a drop in condition occurred and a clear south–north pattern emerged. The drop in condition after the early 1990s was stronger in the northern areas, where Sprat population increased the most. We suggest that the increase in Sprat density in the northern areas, and the consequent spatial differentiation in clupeid condition, have been triggered by the almost total disappearance of the predator cod from the northern Baltic Proper. This study provides a step forward in understanding clupeid condition in the Baltic Sea, presenting evidence that density-dependent mechanisms also operate at the spatial scale within stock units. This stresses the importance of spatio-temporal considerations in the management of exploited fish.
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feeding ecology of central baltic Sprat Sprattus Sprattus larvae in relation to zooplankton dynamics implications for survival
Marine Ecology Progress Series, 2007Co-Authors: M Dickmann, Christian Mollmann, Rüdiger VossAbstract:We investigated the larval feeding ecology of Sprat Sprattus Sprattus L., an important commercial fish species in the Central Baltic Sea. We collected seasonally resolved larval abundance and gut content as well as zooplankton data, with the goal of identifying mechanisms leading to variability in larval survival. Our results show Sprat larvae feed progressively on larger food items as they grow during the season depending on their size and the composition of the available prey. We found first-feeding larvae early in the spawning season to prey exclusively upon microplankton. Small larvae fed mainly upon nauplii of the copepods Acartia spp., Temora longicornis and Centropages hamatus (ca. 65%), whereas larger larvae consumed up to 80% Acartia spp. copepodites and adults, as well as cladocerans. Trends in Sprat larval diets were to a large degree explainable by selective feeding. Feeding success and gut fullness increased linearly with larval size. Trophic niche breadth increased linearly until larvae reached a predator size of 16 mm, after which it decreased. We explain the latter decline by a restricted size spectrum of prey available to larger Sprat larvae, which points towards the importance of considering the structure of the zooplankton community when evaluating the predator size to niche breadth relationship. Our results suggest first-feeding Baltic Sprat larvae to be always food-limited, while larger larvae are not. We hypothesize medium-sized Sprat larvae to be the life stage that has the potential to cause most of the interannual variability in Sprat larval survival, which is dependent on a match between larval production and the state of the plankton cycle.
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recruitment variability in baltic sea Sprat Sprattus Sprattus is tightly coupled to temperature and transport patterns affecting the larval and early juvenile stages
Canadian Journal of Fisheries and Aquatic Sciences, 2006Co-Authors: Hannes Baumann, Friedrich W Koster, Christian Mollmann, Hans-harald Hinrichsen, Arne M Malzahn, Axel TemmingAbstract:Recruitment patterns of Baltic Sea Sprat (Sprattus Sprattus) were correlated to time series of (i) month- and depth-specific temperature conditions and (ii) larval drift patterns inferred from long-term Lagrangian particle simula- tions. From the latter, we derived an index that likely reflected the variable degree of annual larval transport from the central, deep spawning basins to the shallow coastal areas of the Baltic Sea. The drift index was significantly (P < 0.001) correlated to Sprat recruitment success and explained, together with Sprat spawning stock biomass, 82% of the overall variability between 1979 and 2003. Years of strong larval displacement towards southern and eastern Baltic coasts corresponded to relative recruitment failure, while years of retention within the deep basins were associated with relative recruitment success. The strongest correlation between temperature and recruitment occurred during August in surface waters, explaining 73% of the overall variability. Together, the two approaches advocate that new year classes of Baltic Sprat are predominantly composed of individuals born late in the season and are determined in strength mainly by processes acting during the late larval and early juvenile stages. However, prior to be included in recruit- ment predictions, the biological mechanisms underlying these strong correlations may need to be better resolved.
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the influence of hydrography and predation by herring clupea harengus and Sprat Sprattus Sprattus on mesozooplankton long term dynamics in the central baltic sea
(Doctoral thesis PhD) Christian-Albrechts-Universität Institut für Meereskunde Kiel 139 pp, 2006Co-Authors: Christian MollmannAbstract:The present study investigated the long-term dynamics of the copepod species Pseudocalanus elongatus, Temora longicornis and Acartia spp. as well as cladoceran species Bosmina coregoni maritima, Evadne nordmanni and Podon spp. in an environment, i.e. the Central Baltic Sea, characterized by changes in the hydrographic regime and in predation pressure through pelagic clupeids herring (Clupea harengus) and Sprat (Sprattus Sprattus). A clear association between the biomass of P. elongatus and higher salinities, as well as lower temperatures in spring was found, whereas the biomass of T. longicornis and Acartia spp. was positively correlated to water temperature. All cladoceran species also took advantage of higher water temperatures, while decreasing salinity only affected E. nordmanni and Podon spp. The analyses of a predation effect revealed no substantial impact of herring on the mesozooplankton dynamics, whereas a significant predation pressure of Sprat in spring on copepodite stages CV/VI of P. elongatus and T. longicornis was identified. In parallel mortality rates of these copepods increased, which indicates a contribution of the Sprat population to the decline of the P. elongatus and T. longicornis abundance. A limited influence of Sprat predation on the dynamics of cladocerans was detected.
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climate zooplankton and pelagic fish growth in the central baltic sea
Ices Journal of Marine Science, 2005Co-Authors: Christian Mollmann, Marina Fetter, Georgs Kornilovs, Friedrich W KosterAbstract:Oceanographic conditions in the brackish central Baltic Sea are strongly linked to atmospheric forcing and the unusual period of persistently strong westerlies that, since the late 1980s, have resulted in an increase in average water temperatures and decreasing salinity. These changes in temperature and salinity resulted in a change in the dominance of the mesozooplankton community from Pseudocalanus sp. to Temora longicornis and Acartia spp. Similar to the copepod community, the central Baltic fish community shifted from cod (Gadus morhua), dominant during the 1980s, to Sprat (Sprattus Sprattus), dominant during the 1990s. Further, the commercially important pelagic fish species herring (Clupea harengus) and Sprat exhibited reductions in growth. Using Principal Component and Correlation Analyses we investigated the temporal variability in the importance of the food supply as well as competition on condition of central Baltic pelagic fish species. Our results indicate that herring condition results from a combined effect of changes in the food environment and increased competition with Sprat, while Sprat condition appeared to be primarily determined by intra-specific competition.