On 8th May 2019 several researchers from IES and EULS gathered near Lake Auciema to start studying lake food webs complexly and emphasizing the importance of larval fish community studies in the lakes. The general aim of the research is to determine how whole planktonic community structure (all planktonic organisms as potential food items for fish larvae) and aquatic plants in lakes (as the living environment for fish) influence the development of natural fish resources – fish stock development, fish survival and their eating habits.
Video report on the launch of the Auciems lake feed chain research.
Zivju skaits mūsu ezeros samazinās. Viens no iemesliem ir tas, ka kāpura stadijā bojā iet 95% visu zivju mazuļu – daļu apēd citas zivis, bet daudzi cieš arī ūdens kvalitātes dēļ. Zinātnieki no Institute for Environmental Solutions pēta iemeslus un meklē risinājumus šai problēmai, izmantojot arī ezeru apsekošanu no gaisa ar dronu palīdzību. Valsts izglītības attīstības aģentūra PostDoc Latvia Eesti Maaülikool/Estonian University of Life Sciences
Posted by Izziņas Impulss on Monday, May 20, 2019
According to a BBC article that was written 7 years ago – global fish stocks are exploited or exhausted to such an extent that without urgent measures we may be the last generation to catch food from the oceans. Global fish stocks are decreasing – around 85% of global fish stocks are over-exploited, depleted, fully exploited or in recovery from exploitation. Researchers from IES and EULS came together to study how to increase the number of fish in our water bodies. The mortality of newly hatched fish larvae is extremely high, eliminating up to 99% of the brood within a few days after fish first feeding. Fish larvae may die for many reasons but, beside predation, the starvation due to the shortage of suitable food objects (size, morphology) could be one of the main factors of high mortality during the early life stages. If larvae are not able to find suitable food items at the time when yolk-sac feeding ends and they must swap to feed on planktonic food, many of them die from malnutrition, but if food is sufficiently abundant, their survival increases. Therefore, their ability to encounter and intercept food items is critical for their survival and the fate of fish larvae determines the abundance of different cohorts that join later with the adult stocks.
Therefore, researchers from IES and EULS are searching for the reason (and the solution) of the extremely high mortality of fish larvae in Latvia’s and Estonia’s lakes by studying the complexity of the lake food web and applying different novel methods: e.g. assessing larval fish diets via epifluorescence microscopy to see what fish larvae have eaten and is there enough suitable food objects in the lake for fish larvae; developing and testing different equipment and methods (e.g. different nets, flying camera drones) to assess larval fish abundances quantitatively, repeating fish community studies after a year to see how much young fish are left next year (e.g. how strong is their year-class) and finally studying aquatic plants to find out how are macrophytes (as habitat and shelter) structuring the relationships between planktonic communities and fish.
Researchers emphasized that without paying increased attention to the overall exploration of the lake ecosystem, it is not possible to explain how the ecosystem will respond to potential environmental changes and how these changes will affect the overall functioning of the lake ecosystem, especially the development of natural resources – fish stocks and commercial fish species.
The research is part of the project „Fish feeding conditions in lakes with different planktonic food web structure and microvegetation “(MICROFISH), No.220.127.116.11/VIAA/1/18/301. Agreement with State Education Development Agency of the Republic of Latvia No. Programme number 18.104.22.168/16/I/001. The project is financed by the European Regional Development Fund, the State budget of the Republic of Latvia and the foundation „Institute for Environmental Solutions“.
Find out more about the project here.