The Population Development of the Invasive Round Goby Neogobius melanostomus in Latvian Waters of the Baltic Sea

The invasive round goby (Neogobius melanostomus) was established in the coastal waters of the Baltic Sea in the early 1990s. The first observation of the species in Latvian waters was in 2004. In the intervening period, the population grew, the species became of significance for local fisheries, and it likely impacted the local ecosystem in the Baltic Sea. In this study, we characterize the spatial-temporal population development of round goby in Latvian coastal waters using data from three different scientific and fisheries-independent surveys. We also include data from commercial fisheries landings to describe the fisheries targeting the species. Our results suggest an exponential increase in population numbers of round goby in Latvian waters, peaking in 2018, followed by a sharp decline. This observation is also supported by data from commercial fisheries landings. We suggest that intensive commercial fishing had a considerable impact on the rapid decline of the species, but that the decline was potentially amplified through a wider scale decline, as observed in many areas of the Baltic Sea. The results of this study contribute to the knowledge base on the species and how fisheries can aid in limiting the development of invasive fish populations. Based on the results of the study, we also provide recommendations for better future monitoring of the species in the coastal waters of the Baltic Sea

Increases of opportunistic species in response to ecosystem change:The case of the Baltic Sea three-spined stickleback

Under rapid environmental change, opportunistic species may exhibit dramatic increases in response to the altered conditions, and can in turn have large impacts on the ecosystem. One such species is the three-spined stickleback (Gasterosteus aculeatus), which has shown substantial increases in several aquatic systems in recent decades. Here, we review the population development of the stickleback in the Baltic Sea, a large brackish water ecosystem subject to rapid environmental change. Current evidence points to predatory release being the central driver of the population increases observed in some areas, while both eutrophication and climate change have likely contributed to creating more favourable conditions for the stickleback. The increasing stickleback densities have had profound effects on coastal ecosystem function by impairing the recruitment of piscivorous fish and enhancing the effects of eutrophication through promoting the production of filamentous algae. The increase poses a challenge for both environmental management and fisheries, where a substantial interest from the pelagic fisheries fleet in exploiting the species calls for urgent attention. While significant knowledge gaps remain, we suggest that the case of the Baltic Sea stickleback increase provides generalisable lessons of value for understanding and managing other coastal ecosystems under rapid change

Essential coastal habitats for fish in the Baltic Sea

Many coastal and offshore fish species are highly dependent on specific habitat types for population maintenance. In the Baltic Sea, shallow productive habitats in the coastal zone such as wetlands, vegetated flads/lagoons and sheltered bays as well as more exposed rocky and sandy areas are utilized by fish across many life history stages including spawning, juvenile development, feeding and migration. Although there is general consensus about the critical importance of these essential fish habitats (EFH) for fish production along the coast, direct quantitative evidence for their specific roles in population growth and maintenance is still scarce. Nevertheless, for some coastal species, indirect evidence exists, and in many cases, sufficient data are also available to carry out further quantitative analyses. As coastal EFH in the Baltic Sea are often found in areas that are highly utilized and valued by humans, they are subjected to many different pressures. While cumulative pressures, such as eutrophication, coastal construction and development, climate change, invasive species and fisheries, impact fish in coastal areas, the conservation coverage for EFH in these areas remains poor. This is mainly due to the fact that historically, fisheries management and nature conservation are not integrated neither in research nor in management in Baltic Sea countries. Setting joint objectives for fisheries management and nature conservation would hence be pivotal for improved protection of EFH in the Baltic Sea. To properly inform management, improvements in the development of monitoring strategies and mapping methodology for EFH are also needed. Stronger international cooperation between Baltic Sea states will facilitate improved management outcomes across ecologically arbitrary boundaries. This is especially important for successful implementation of international agreements and legislative directives such as the Baltic Sea Action Plan, the Marine Strategy Framework Directive, the Habitats Directive, and the Maritime Spatial Planning Directive, but also for improving the communication of information related to coastal EFH among researchers, stakeholders, managers and decision makers. In this paper, efforts are made to characterize coastal EFH in the Baltic Sea, their importance and the threats/pressures they face, as well as their current conservation status, while highlighting knowledge gaps and outlining perspectives for future work in an ecosystem-based management framework. (C) 2018 Elsevier Ltd. All rights reserved.Peer reviewe

Usage of visual models in the teaching-learning process of biology and geography in school

Pētījuma tēma ir uzskates modeļu izmantošana bioloģijas un ģeogrāfijas apguvē skolā. Pētījumā tiek noskaidrotas mūsdienīga mācību procesa dabaszinātnēs pamatnostādnes un pamatota modeļu izmantošanas nepieciešamība, kas balstīta zinātniskajā literatūrā pedagoģijā un iepriekš veiktajos pētījumos par modeļu izmantošanu mācību satura apguvē. Autore darbā piedāvā konkrētus modeļu piemērus bioloģijā un ģeogrāfijā. Empīriskā pētījuma rezultāti parāda, ka, izmantojot ekosistēmas modeļa izgatavošanu un skaidrojot modeli, skolēni demonstrēja izpratni par pētīto ekosistēmu un tās komponentiem. Skolēni pauda pozitīvu attieksmi pret izmantoto metodi, izrādīja interesi savas apkārtnes ekosistēmas pētīšanā un radošumu tās attēlošanā ar modeļa palīdzību. Darba nobeigumā autore pauž galvenos secinājumus par veikto pētījumu. Atslēgas vārdi: modeļi, uzskates modeļi, vizualizācija, mācību process bioloģijā un ģeogrāfijāResearch is about usage of visual models in the teaching-learning process of biology and geography in school. In research author clarifies the basic statements of teaching-learning process of science in nowadays and confirms the usage of visual models in teaching-learning process based on scientific pedagogical literature and previous researches of model using in schools. Author gives examples of visual models in biology and geography. Results of empirical research indicated that students demonstrated good comprehension about different ecosystems and its intricate components after making and explaining visual models of those ecosystems. Students also had positive attitudes toward the opportunity to research local ecosystems and visualise them in models as a study strategy. In conclusion author gives the main ideas which have been proved. Keywords: models, visual models, biology, geography, visualizatio

Seasonal changes in feeding ecology of fish in lake Burtnieks in 2013

Briekmane L. Zivju sezonālās barošanās ekoloģija Burtnieku ezerā 2013. gadā. Maģistra darba mērķis ir raksturot zivju barošanos Burtnieku ezerā dažādās sezonās. 2013. gadā trīs dažādās sezonās kopumā tika analizēti 450 zivju barošanās paraugi no 13 zivju sugām. No iegūtajiem datiem tika aprēķināta katra barības objekta procentuālais īpatsvars pēc biomasas, kā arī aprēķināts barības objekta relatīvā nozīmīguma indekss zivju barībā dažādās sezonās un zivju garuma klasēs. 255 zivju kuņģos tika atrasti barības objekti. Klāsteranalīzes rezultāti zivis pēc to barības objektiem iedalīja sekojošās grupās: bentivoras, herbivoras, planktivoras un plēsīgas zivis. Atsevišķas sugas dažādās sezonās atradās dažādās barošanās grupās, norādot uz sezonālām izmaiņām barošanās ekoloģijā. ANOSIM analīze parādīja, ka statistiski būtiskas atšķirības pastāv starp raudu un plaužu barošanos dažādās sezonās, kā arī starp raudu, plaužu, asaru un ruduļu barošanos dažādās garuma klasēs. Atslēgvārdi: zivju barošanās, ezeri, sezonālas izmaiņasBriekmane L. 2014. „Seasonal changes in feeding ecology of fish in Lake Burtnieks in 2013”. The aim of this masters thesis is to describe feeding ecology of fishes in Lake Burtnieks in different seasons. 13 fish species were sampled with gillnets in Lake Burtnieks and stomach contents of 450 fishes were examined. The percentage by total biomass and index of relative importance (IRI) of each prey category was calculated separately for each season and lenght class. 255 stomachs contained food items. Cluster-analysis divided fishes in groups according to their prey items in different seasons – bentivores, herbivores, zooplanktivores and piscivores. Some species showed switching from one group to other in different seasons. ANOSIM analysis showed significant differences in feeding ecology of roach and bream in different seasons and in roach, bream, perch an rudd between lenght classes, which can be associated with changing availability in food resources in each season and diet shifts during ontogenesis. Key words: fish feeding, shallow lakes, seasonal change

The Population Development of the Invasive Round Goby <i>Neogobius melanostomus</i> in Latvian Waters of the Baltic Sea

The invasive round goby (Neogobius melanostomus) was established in the coastal waters of the Baltic Sea in the early 1990s. The first observation of the species in Latvian waters was in 2004. In the intervening period, the population grew, the species became of significance for local fisheries, and it likely impacted the local ecosystem in the Baltic Sea. In this study, we characterize the spatial–temporal population development of round goby in Latvian coastal waters using data from three different scientific and fisheries-independent surveys. We also include data from commercial fisheries landings to describe the fisheries targeting the species. Our results suggest an exponential increase in population numbers of round goby in Latvian waters, peaking in 2018, followed by a sharp decline. This observation is also supported by data from commercial fisheries landings. We suggest that intensive commercial fishing had a considerable impact on the rapid decline of the species, but that the decline was potentially amplified through a wider scale decline, as observed in many areas of the Baltic Sea. The results of this study contribute to the knowledge base on the species and how fisheries can aid in limiting the development of invasive fish populations. Based on the results of the study, we also provide recommendations for better future monitoring of the species in the coastal waters of the Baltic Sea

A pan-Baltic assessment of temporal trends in coastal pike populations

The northern pike (Esox lucius) is an iconic predatory fish species of significant recreational value and ecological role in the Baltic Sea. Some earlier studies indicate local declines of pike in the region, but a thorough spatial evaluation of regional population trends of pike in the Baltic Sea is lacking. In this study, we collate data from 59 unique time-series from fisheries landings and fishery-independent monitoring programs to address temporal trends in pike populations since the mid-2000 ' s in eight countries surrounding the Baltic Sea. In a common analysis considering all time-series in concert, we found indications of an overall regional temporal decline of pike in the Baltic Sea, but trends differed among countries. Individual negative trends in time-series were moreover found in several regions of the Baltic Sea, but predominantly so in the central and southern parts, while positive trends were only found in Estonia and northern Finland. The mix of data used in this study is inherently noisy and to some extent of uncertain quality, but as a result of the overall negative trends, together with the socioeconomic and ecological importance of pike in coastal areas of the Baltic Sea, we suggest that actions should be taken to protect and restore pike populations. Management measures should be performed in combination with improved fishery-independent monitoring programs to provide data of better quality and development of citizen-science approaches as a data source for population estimates. Possible measures that could strengthen pike populations include harvest regulations (including size limits, no-take areas and spawning closures), habitat protection and restoration, and an ecosystem-based approach to management considering also the impact of natural predators

A pan-Baltic assessment of temporal trends in coastal pike populations

The northern pike (Esox lucius) is an iconic predatory fish species of significant recreational value and ecological role in the Baltic Sea. Some earlier studies indicate local declines of pike in the region, but a thorough spatial evaluation of regional population trends of pike in the Baltic Sea is lacking. In this study, we collate data from 59 unique time-series from fisheries landings and fishery-independent monitoring programs to address temporal trends in pike populations since the mid-2000′s in eight countries surrounding the Baltic Sea. In a common analysis considering all time-series in concert, we found indications of an overall regional temporal decline of pike in the Baltic Sea, but trends differed among countries. Individual negative trends in time-series were moreover found in several regions of the Baltic Sea, but predominantly so in the central and southern parts, while positive trends were only found in Estonia and northern Finland. The mix of data used in this study is inherently noisy and to some extent of uncertain quality, but as a result of the overall negative trends, together with the socioeconomic and ecological importance of pike in coastal areas of the Baltic Sea, we suggest that actions should be taken to protect and restore pike populations. Management measures should be performed in combination with improved fishery-independent monitoring programs to provide data of better quality and development of citizen-science approaches as a data source for population estimates. Possible measures that could strengthen pike populations include harvest regulations (including size limits, no-take areas and spawning closures), habitat protection and restoration, and an ecosystem-based approach to management considering also the impact of natural predators

A pan-Baltic assessment of temporal trends in coastal pike populations

The northern pike (Esox lucius) is an iconic predatory fish species of significant recreational value and ecological role in the Baltic Sea. Some earlier studies indicate local declines of pike in the region, but a thorough spatial evaluation of regional population trends of pike in the Baltic Sea is lacking. In this study, we collate data from 59 unique time-series from fisheries landings and fishery-independent monitoring programs to address temporal trends in pike populations since the mid-2000′s in eight countries surrounding the Baltic Sea. In a common analysis considering all time-series in concert, we found indications of an overall regional temporal decline of pike in the Baltic Sea, but trends differed among countries. Individual negative trends in time-series were moreover found in several regions of the Baltic Sea, but predominantly so in the central and southern parts, while positive trends were only found in Estonia and northern Finland. The mix of data used in this study is inherently noisy and to some extent of uncertain quality, but as a result of the overall negative trends, together with the socioeconomic and ecological importance of pike in coastal areas of the Baltic Sea, we suggest that actions should be taken to protect and restore pike populations. Management measures should be performed in combination with improved fishery-independent monitoring programs to provide data of better quality and development of citizen-science approaches as a data source for population estimates. Possible measures that could strengthen pike populations include harvest regulations (including size limits, no-take areas and spawning closures), habitat protection and restoration, and an ecosystem-based approach to management considering also the impact of natural predators