Incorporating environmental variability in stock assessment: predicting recruitment, spawner biomass, and landings of sprat (Sprattus sprattus) in the Baltic Sea

2008 ◽  
Vol 65 (7) ◽  
pp. 1334-1341 ◽  
Author(s):  
Brian R. MacKenzie ◽  
Jan Horbowy ◽  
Fritz W. Köster
Keyword(s):  
Baltic Sea ◽  
Environmental Variability ◽  
Positive Impact ◽  
Stock Assessment ◽  
Assessment Procedure ◽  
The Baltic Sea ◽  
Sprattus Sprattus ◽  
Stock Biomass ◽  
Spawning Stock ◽  
The Baltic

Temperature has a significant positive impact on recruitment of sprat, Sprattus sprattus, in the Baltic Sea. Here we evaluate whether an existing recruitment model for the year classes 1973–1999 can forecast recruitment for five new year classes. The coefficient of variation (CV) of predictions was 5%, and four of five new year classes were within 95% confidence limits of predictions made by the earlier model. We then assimilated climatic, oceanographic, and recruitment linkages and their uncertainty into the standard International Council for the Exploration of the Sea (ICES) assessment procedure to predict key advisory-related variables such as spawning stock biomass (SSB) and landings. These linkages enable a forecast of recruitment earlier than the annual assessment meeting. Forecasts made using the North Atlantic Oscillation to predict the 2006 year class showed that spawner biomass would be 15% lower than spawner biomass calculated using the ICES standard methodology. The difference in perception of future biomass does not affect the advice for the stock because the spawning stock biomass is greater than the critical biomass limit (SSB > BPA). However, when this is not the case or when it is desirable to broaden the ecosystem basis for fisheries management, incorporation of knowledge of recruitment processes may be beneficial.

scholarly journals Oxygen depletion in coastal seas and the effective spawning stock biomass of an exploited fish species

2016 ◽  
Vol 3 (1) ◽  
pp. 150338 ◽  
Author(s):  
H.-H. Hinrichsen ◽  
B. von Dewitz ◽  
J. Dierking ◽  
H. Haslob ◽  
A. Makarchouk ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Environmental Conditions ◽  
Size Structure ◽  
Oxygen Depletion ◽  
The Baltic Sea ◽  
Egg Survival ◽  
Stock Biomass ◽  
Spawning Stock ◽  
The Baltic ◽  
Baltic Cod

Environmental conditions may have previously underappreciated effects on the reproductive processes of commercially exploited fish populations, for example eastern Baltic cod, that are living at the physiological limits of their distribution. In the Baltic Sea, salinity affects neutral egg buoyancy, which is positively correlated with egg survival, as only water layers away from the oxygen consumption-dominated sea bottom contain sufficient oxygen. Egg buoyancy is positively correlated to female spawner age/size. From observations in the Baltic Sea, a field-based relationship between egg diameter and buoyancy (floating depth) could be established. Hence, based on the age structure of the spawning stock, we quantify the number of effective spawners, which are able to reproduce under ambient hydrographic conditions. For the time period 1993–2010, our results revealed large variations in the horizontal extent of spawning habitat (1000–20 000 km 2 ) and oxygen-dependent egg survival (10–80%). The novel concept of an effective spawning stock biomass takes into account offspring that survive depending on the spawning stock age/size structure, if reproductive success is related to egg buoyancy and the extent of hypoxic areas. Effective spawning stock biomass reflected the role of environmental conditions for Baltic cod recruitment better than the spawning stock biomass alone, highlighting the importance of including environmental information in ecosystem-based management approaches.

scholarly journals The role of climate and fisheries on the temporal changes in the Bothnian Bay foodweb

2016 ◽  
Vol 73 (7) ◽  
pp. 1739-1749 ◽  
Author(s):  
Zeynep Pekcan-Hekim ◽  
Anna Gårdmark ◽  
Agnes M. L. Karlson ◽  
Pirkko Kauppila ◽  
Mikaela Bergenius ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Trophic Levels ◽  
Strong Increase ◽  
The Baltic Sea ◽  
Key Species ◽  
Long Term Changes ◽  
Spawning Stock ◽  
The Baltic ◽  
Bothnian Bay

Abstract Climate change, eutrophication, and fishing are main pressures associated with changes in the abiotic and biotic environment in several sub-basins of the Baltic Sea. Identifying the nature of such changes is of relative importance for fisheries and environmental management. The Bothnian Bay is the northernmost sub-basin in the Baltic Sea and the responses of the foodweb to long-term changes in combined pressures have not been investigated. In this study, we explore long-term changes in the Bothnian Bay foodweb, represented by key species across all trophic levels over the past 34 years, and identify potential environmental and anthropogenic drivers. The results indicate that salinity is the most important driver to explain changes in the composition of the offshore biota in the Bothnian Bay. These changes are probably driven by indirect effects of salinity rather than bottom-up effects. A decline in the herring spawning-stock biomass was most plausibly attributed to an increased competition for food due to a parallel increase in vendace, which uses the same food resources (zooplankton and zoobenthos) and may benefit from declining salinity due to its limnic origin. A strong increase in the abundance of grey seal and ringed seal populations was seen in the late 2000s but was not related to any of the pressure variables analysed. Temperature and nutrients were not identified as important drivers of changes in the overall biota. Our study explores correlative relationships between variables and identifies potential interactions in the foodweb to generate hypotheses for further studies.

scholarly journals Stock assessment of the Baltic Sea fish in the ICES Working Groups

Trudy VNIRO ◽  
2018 ◽  
Vol 174 ◽  
pp. 58-71
Author(s):  
V. М. Amosov ◽  
◽  
А. S. Zezera ◽  
A. I. Karpushevskaia ◽  
T. G. Vasilijeva ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Stock Assessment ◽  
The Baltic Sea ◽  
Working Groups ◽  
The Baltic ◽  
Sea Fish

scholarly journals Reconstructing the population dynamics of sprat (Sprattus sprattus balticus) in the Baltic Sea in the 20th century

2012 ◽  
Vol 69 (6) ◽  
pp. 1010-1018 ◽  
Author(s):  
Margit Eero
Keyword(s):  
Population Dynamics ◽  
Baltic Sea ◽  
20Th Century ◽  
Human Impacts ◽  
Management Strategies ◽  
The Baltic Sea ◽  
Sprattus Sprattus ◽  
1960S And 1970S ◽  
The 1960S ◽  
The Baltic

Abstract Eero, M. 2012. Reconstructing the population dynamics of sprat (Sprattus sprattus balticus) in the Baltic Sea in the 20th century. – ICES Journal of Marine Science, 69: 1010–1018 . Long time-series of population dynamics are increasingly needed in order to understand human impacts on marine ecosystems and support their sustainable management. In this study, the estimates of sprat (Sprattus sprattus balticus) biomass in the Baltic Sea were extended back from the beginning of ICES stock assessments in 1974 to the early 1900s. The analyses identified peaks in sprat spawner biomass in the beginning of the 1930s, 1960s, and 1970s at ∼900 kt. Only a half of that biomass was estimated for the late 1930s, for the period from the late 1940s to the mid-1950s, and for the mid-1960s. For the 1900s, fisheries landings suggest a relatively high biomass, similar to the early 1930s. The exploitation rate of sprat was low until the development of pelagic fisheries in the 1960s. Spatially resolved analyses from the 1960s onwards demonstrate changes in the distribution of sprat biomass over time. The average body weight of sprat by age in the 1950s to 1970s was higher than at present, but lower than during the 1980s to 1990s. The results of this study facilitate new analyses of the effects of climate, predation, and anthropogenic drivers on sprat, and contribute to setting long-term management strategies for the Baltic Sea.

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