Vides mainības un zvejas ietekme uz Baltijas mencas (Gadus morhua callarias L.) paaudžu ražību

Elektroniskā versija nesatur pielikumusPromocijas darbā tiek novērtēta mencas ikru izdzīvošanu noteicošo hidroloģisko parametru mainība laikā un telpā trīs galvenajās nārsta vietās Baltijas jūrā –Bornholmas, Gdaņskas un Gotlandes ieplakās. Tiek definēta mencas nārsta dzīvotne jeb „vairošanās tilpums”(RV): ūdens tilpums katrā no nārsta vietām, kurā izšķīdušā skābekļa saturs ir lielāks par 2 ml l-1 un ūdens sāļums lielāks par 11psu, kas nodrošina mencas ikru labvēlīgu attīstību. Mencas RV dinamika un to nosakošie hidroloģiskie procesi Baltijas jūrā tiek analizēti saistībā ar klimata mainību. Lai novērtētu mencas biomasas un papildinājuma dinamiku, aprēķinātais RV tiek testēts kā vides mainīgais krājuma papildinājuma klasiskajā Rikera krājuma papildinājuma modelī. Papildus tam darbā tiek analizēta mencas kanibālisma loma ikgadējā krājuma -papildinājuma dinamikā. Darbs ir piecu publikāciju kopsavilkums. Darbs izstrādāts Latvijas Zivsaimniecības pētniecības institūtā ”LATFRI”, Pārtikas drošības dzīvnieku veselības un vides zinātniskajā institūtā „BIOR”, Ķīles Universitātes Jūras Pētniecības institūtā (Vācija) un Latvijas Universitātes Bioloģijas fakultātes Hidrobioloģijas un Zooloģijas un dzīvnieku ekoloģijas katedrās.This thesis assesses spatial and temporal variability in conditions affecting the survival of cod eggs in three distinct spawning sites in the Baltic Sea – Bornholm, Gdansk and Gotland. The cod reproduction habitat or so called 'reproductive volume' (RV) at each of the spawning sites is defined as the volume of water where salinity is higher than 11psu and dissolved oxygen content higher than 2ml l-1 permitting successful egg development. Cod RV annual dynamic and the factors determining it is analyzed in connection with climate change in the Baltic Sea. In order to assess cod biomass and recruitment dynamics the calculated RV are being tested as the environmental variables in the classical Ricker stock recruitment model. In addition, the influence of cannibalism on annual stock recruitment dynamics is analyzed. The thesis is summary of five publications. The study underpaying proposed Doctoral thesis is carried out in Latvian Fisheries Research Institute (LATFRI), Institute of Food Safety, Animal Health and Environment (BIOR), Institute of Marine Science (IFM) at University of Kiel (Germany) and Departments of Hydrobiology and Zoology and Animal Ecology of Faculty of Biology, Latvian University

IMPACT OF ENVIRONMENTAL VARIABILITY ON YEAR-CLASS STRENGTH OF BALTIC COD (GADUS MORHUA CALLLARIAS L.)

ANOTĀCIJA Promocijas darbā tiek novērtēta mencas ikru izdzīvošanu noteicošo hidroloģisko parametru mainība laikā un telpā trīs galvenajās nārsta vietās Baltijas jūrā –Bornholmas, Gdaņskas un Gotlandes ieplakās. Tiek definēta mencas nārsta dzīvotne jeb „vairošanās tilpums”(RV): ūdens tilpums katrā no nārsta vietām, kurā izšķīdušā skābekļa saturs ir lielāks par 2 ml l-1 un ūdens sāļums lielāks par 11psu, kas nodrošina mencas ikru labvēlīgu attīstību. Mencas RV dinamika un to nosakošie hidroloģiskie procesi Baltijas jūrā tiek analizēti saistībā ar klimata mainību. Lai novērtētu mencas biomasas un papildinājuma dinamiku, aprēķinātais RV tiek testēts kā vides mainīgais krājuma papildinājuma klasiskajā Rikera krājuma papildinājuma modelī. Papildus tam darbā tiek analizēta mencas kanibālisma loma ikgadējā krājuma -papildinājuma dinamikā. Darbs ir piecu publikāciju kopsavilkums. Darbs izstrādāts Latvijas Zivsaimniecības pētniecības institūtā ”LATFRI”, Pārtikas drošības dzīvnieku veselības un vides zinātniskajā institūtā „BIOR”, Ķīles Universitātes Jūras Pētniecības institūtā (Vācija) un Latvijas Universitātes Bioloģijas fakultātes Hidrobioloģijas un Zooloģijas un dzīvnieku ekoloģijas katedrās. Atslēgas vārdi: Baltijas jūras menca, papildinājums, vairošanās tilpums, krājuma – papildinājuma attiecības, kanibālisms.ANNOTATION This thesis assesses spatial and temporal variability in conditions affecting the survival of cod eggs in three distinct spawning sites in the Baltic Sea – Bornholm, Gdansk and Gotland. The cod reproduction habitat or so called 'reproductive volume' (RV) at each of the spawning sites is defined as the volume of water where salinity is higher than 11psu and dissolved oxygen content higher than 2ml l-1 permitting successful egg development. Cod RV annual dynamic and the factors determining it is analyzed in connection with climate change in the Baltic Sea. In order to assess cod biomass and recruitment dynamics the calculated RV are being tested as the environmental variables in the classical Ricker stock recruitment model. In addition, the influence of cannibalism on annual stock recruitment dynamics is analyzed. The thesis is summary of five publications. The study underpaying proposed Doctoral thesis is carried out in Latvian Fisheries Research Institute (LATFRI), Institute of Food Safety, Animal Health and Environment (BIOR), Institute of Marine Science (IFM) at University of Kiel (Germany) and Departments of Hydrobiology and Zoology and Animal Ecology of Faculty of Biology, Latvian University. Key words: Baltic cod, recruitment, reproduction volume, stock – recruitment relationship, cannibalism

Working Group on Bycatch of Protected Species (WGBYC)

WGBYC planned to address seven Terms of Reference, one of which was a special request from the European Commission on emergency bycatch mitigation measures for common dolphin in the Bay of Biscay and harbour porpoise in the Baltic Sea (ToR G). ToR G demanded a great deal of resources from WGBYC and, coupled with the COVID–19 disruption where WGBYC work had to be carried out remotely, this meant it was not possible to complete all tasks. The 2020 report is structured in the same order as the ToRs. Note that ToR E was not addressed while ToR G is reported in WKEMBYC (2020). All data submissions were requested via a formal WGBYC/ICES data call (Annex 6: below). The data call requested data on fishing effort, monitoring effort and PETS (protected, endangered, and threatened species of marine mammals, seabirds, reptiles, and fish) bycatch incidents in 2018. 19 of the 24 countries that contacted (18 ICES countries and 6 Mediterranean non-ICES countries) responded. WGBYC did not accept data brought to the meeting, but where problems were found during assessments with country submissions, updated versions were accepted. The quality and scope of Member States (MS) reports on the implementation of Regulation 812/2004 (cetacean bycatch) during 2018 remain varied (ToR A). Most countries have relied on monitoring through their DCF sampling programmes rather than implementing dedicated ob-server programmes. This means that métiers that pose the greatest risk of cetacean bycatch are generally under-sampled and bycatch is underestimated. Regulation 812/2004 was repealed and replaced in June 2019 by the Technical Conservation Measures Regulation (Regulation (EU) 2019/1241) and PETS bycatch monitoring is further implemented through the EU-MAP (Regula-tion (EU) 2017/1004). For 2018, data received through the WGBYC data call amounted to 82 cetaceans (5 species); 175 seals (4 species), 696 birds (at least 22 species); 37 644 elasmobranchs (at least 49 species); 2061 teleost fish (9 species) and 134 turtles (at least 2 species). Equivalent data from non-EU countries was also received from the USA and Iceland. Bycatch of marine mammals was observed in all ecoregions and several gears including gillnets, traps, longlines, and trawls. Seabirds were by-caught in most ecoregions, mainly in nets and longlines. In 2018, bycaught marine turtles were recorded mostly in set nets and trawls in the Mediterranean and in longlines in the Azores. High bycatch rates were observed for some elasmobranch species which are of conservation concern, particularly in trawl gears in the Celtic Sea, the Greater North Sea and Western Mediterranean, and nets in the Celtic Sea. In the US Northwest Atlantic, the gear of most concern are set nets for marine mammals and sea turtles. The gears of most concern in Iceland are set nets (birds and marine mammals) and longlines (birds). Eight countries also contributed numbers of bycaught stranded cetaceans. Bycatch was the predominant cause of death of common dolphins stranded in the Bay of Biscay and Channel. Member states compliance with the ‘pinger’ requirements of Regulation 812/2004 is difficult to gauge from the submitted reports due to reporting inconsistencies and incomplete information (ToR B). Only the United Kingdom appears to comply fully, reporting that all relevant vessels are equipped with “DDD” pingers used under a derogation and there is active enforcement in place. But in general, there has been little progress in the mitigation of cetacean bycatch and the effectiveness of pingers appears to vary among fishing métiers and geographical areas. WGBYC continues to have insufficient data to examine bycatch rates according to pinger use within their database