Henn Ojaveer

University of Tartu · Pärnu College

The introduction of harmful aquatic organisms and pathogens (HAOP) via the ballast water of ships can endanger human health, the environment, economic resource-related systems, as well as impair biological diversity. Early warning systems (EWS) are highly effective instruments for mitigating risks and enhancing readiness in the face of potential di...

Fish stocks composed of several populations are considered to have more stable productivity than stocks containing only one or few populations. This stability is attributed to complementary or independent dynamics among the populations within the stock—the so-called portfolio effect. Declines of populations within stocks that have delayed recovery...

Current methods for assessing the environmental impacts of marine non-indigenous species (NIS) are limited by insufficient data, an over-reliance on expert judgement and too coarse a spatial resolution, which hampers accurate local management. However, advances in data-driven analyses offer significant potential for developing more comprehensive an...

The Workshop on Bay of Biscay and Iberian Coast Aquaculture Overview (WKBoBICAO) was established to assemble and synthesize aquaculture related data and information and to inform the aquaculture overview for this ecoregion

Although invasive alien species have long been recognized as a major threat to nature and people, until now there has been no comprehensive global review of the status, trends, drivers, impacts, management and governance challenges of biological invasions. The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES)...

Aim Retrospective (pre‐ vs. post‐invasion) and cross‐sectional comparisons of ecosystems exposed to high and low bioinvasion pressure, provide an alternative approach to evaluate shifts in biological communities associated with non‐indigenous species (NIS) introductions. In this study, we aimed to examine general patterns of change in community com...

Fisheries overviews summarize fishing activities in ICES ecoregions, including describing which countries are catching what species, the various fishing methods being used, the distribution and intensity of fishing, the status of fished stocks, how stocks are managed, and what the impacts of fisheries on the ecosystem are. Fisheries overviews ar...

The Workshop on pathways to climate-aware advice (WKCLIMAD) met in the autumn of 2021 to develop a proposal for an advisory framework that accounts for the influences of climate change on aquaculture, fisheries, and ecosystems. The workshop worked through online ses-sions with over 40 participants. Climate-informed advice should be provided through...

We developed and validated a mixed-stock analysis (MSA) method with 59 single-nucleotide polymorphisms selected from genome-wide data to assign individuals to populations in mixed-stock samples of Atlantic herring from the North and Baltic seas. We analysed 3734 herring from spawning locations and scientific catches of mixed feeding stocks to demon...

Ecosystem services (ES) are the benefits natural ecosystems provide to society, such as food provisioning, water supply, climate regulation and recreational benefits. Biological invasions are a major driver of global change, and several non-indigenous species (NIS) may alter key ecological feedbacks with ultimate consequences to ES, livelihoods and...

The Workshop on Celtic Seas Aquaculture Overview (WKCSAO) was established to assemble and synthesize aquaculture related data and information from the Celtic Seas ecoregion to inform the Celtic Seas ecoregion aquaculture overview. The Celtic Seas ecoregion comprises much of the UK and all Ireland. Aquaculture is practised in all coastal waters. Bot...

The aim of the Workshop on Stickleback and Round Goby in the Baltic Sea (WKSTARGATE) was to update, summarize and synthesize the current knowledge of both species with respect to their ecology and potential use in fisheries. Ongoing projects were presented in the mornings of the first two days to inform participants about current research in the re...

The main aim of WKVMEBM 2022 was to develop and document an operational evidence-based procedure for the production of recurrent ICES advice on VMEs.

Recent global trade disruptions, due to blockage of the Suez Canal and cascading effects of COVID-19, have altered the movement patterns of commercial ships and may increase worldwide invasions of marine non-indigenous species. Organisms settle on the hulls and underwater surfaces of vessels and can accumulate rapidly, especially when vessels remai...

Native to the Ponto-Caspian region, the benthic round goby (Neogobius melanostomus) has invaded several European inland waterbodies as well as the North American Great Lakes and the Baltic Sea. The species is capable of reaching very high densities in the invaded ecosystems, with not only evidence for significant food-web effects on the native biot...

Incorporation of ecosystem information into fish stock assessments and management advice, a cornerstone of delivering ecosystem-based fisheries management (EBFM), occurs often implicitly, faces multiple challenges, and remains often unquantified in terms of scope and scale. This paper provides a comprehensive overview of the inclusion of ecosystem...

Case studies in support of Caswell et al. 2020.

Food webs are central entities mediating processes and external pressures in marine ecosystems. They are essential to understand and predict ecosystem dynamics and provision of ecosystem services. Paradoxically, utilization of food web knowledge in marine environmental conservation and resource management is limited. To better understand the use of...

The ocean provides essential services to human wellbeing through climate regulation, provision of food, energy and livelihoods, protection of communities and nurturing of social and cultural values. Yet despite the ocean’s key role for all life, it is failing as a result of unsustainable human practices. The first global integrated assessment of th...

Scientific interest in the dynamics of fish recruitment dates back to the beginning of the 20th century. Since then, several studies have shown that the environment may have a stronger effect on recruitment (R) compared to that of the spawning stock biomass (SSB). By combining a suite of methods designed to detect the nonlinear, nonstationary and i...

The threat posed by invasive non-native species worldwide requires a global approach to identify which introduced species are likely to pose an elevated risk of impact to native species and ecosystems. To inform policy, stakeholders and management decisions on global threats to aquatic ecosystems, 195 assessors representing 120 risk assessment area...

KEYNOTE POINTS 1. Understanding of the ocean continues to improve. Innovations in sensors andautonomous observation platforms have substantially increased observations of the ocean. Regional observation programmes have expanded, with better coordination and integration. 2. Some responses for mitigating or reducing pressures and their associated...

KEYNOTE POINTS 1. Innovations in technology and engineering regarding sensors and autonomous observation platforms have substantially increased observations of the ocean and allowed for those observations to be collected at finer temporal and spatial resolutions. 2.The networking and coordination of regional observation programmes has been promote...

KEYNOTE POINTS 1. The purpose of the second World Ocean Assessment is to update the first World Ocean Assessment by providing an understanding of changes that have occurred in the global ocean since 2010 and associated trends. 2. The Assessment also provides an overview of understanding of some aspects not fully covered in the first Assessment, s...

The introduction of non-indigenous species (NIS) is a major driver for global change in species biogeography, often associated with significant consequences for recipient ecosystems and services they provide for humans. Despite mandated by several high-level international legislative instruments, comprehensive quantitative evaluation on ecosystem i...

- The Mobilization of existing data and the development of tools and open, global repositories provide a global picture of the diversity of marine fishes, with 17762 known species, including 238 species described since the first World Ocean Assessment (United Nations, 2017) - While knowledge of the biodiversity of marine fishes exceeds that of many...

Studying how food web structure and function vary through time represents an opportunity to better comprehend and anticipate ecosystem changes. Yet, temporal studies of highly resolved food web structure are scarce. With few exceptions, most temporal food web studies are either too simplified, preventing a detailed assessment of structural properti...

Improving the health of coastal and open sea marine ecosystems represents a substantial challenge for sustainable marine resource management, since it requires balancing human benefits and impacts on the ocean. This challenge is often exacerbated by incomplete knowledge and lack of tools that measure ocean and coastal ecosystem health in a way that...

Quantification and attribution of the food web changes associated with the invasion of non-indigenous species in the marine realm often remain a challenge. One of the pelagic non-indigenous species of concern in the recent history of aquatic bioinvasions is the predatory cladoceran Cercopagis pengoi, which invaded the Baltic Sea in the early 1990s....

Aim The introduction of aquatic non‐indigenous species (ANS) has become a major driver for global changes in species biogeography. We examined spatial patterns and temporal trends of ANS detections since 1965 to inform conservation policy and management. Location Global. Methods We assembled an extensive dataset of first records of detection of A...

To understand the restoration potential of degraded habitats, it is important to know the key processes and habitat features that allow for recovery after disturbance. As part of the EU (Horizon 2020) funded MERCES project, a group of European experts compiled and assessed current knowledge, from both past and ongoing restoration efforts, within th...

The concept of ‘blue growth’, which aims to promote the growth of ocean economies whilst holistically managing marine socio-ecological systems, is emerging within national and international marine policy. The concept is often promoted as being novel, however, we show that, historical analogies exist which can provide insights for contemporary plann...

1. The disproportionately low presence of marine species in the list of invasive alien species (IAS) of Union concern of the European Union (EU) Regulation 1143/2014 does not fully acknowledge the threat they pose to the EU marine environment. 2. In this study, the first EU-scale Horizon Scanning (HS) focusing on marine alien species was performed,...

Ecosystem-based management requires an assessment of the cumulative effects of human pressures and environmental change. The operationalization and integration of cumulative effects assessments (CEA) into decision-making processes often lacks a comprehensive and transparent framework. A risk-based CEA framework that divides a CEA in risk identifica...

Parasites may play several critical functions in marine ecosystems, including possibly influencing introduction success or modifying the roles of non-indigenous species. Based on seasonally replicated sampling, we have investigated parasite communities and infection rates of the non-indigenous round goby Neogobius melanostomus in two localities in...

The Ballast Water Management Convention adopted at the International Maritime Organization (IMO) allows exemptions from ballast water management requirements. These exemptions may be granted when a risk assessment results in an acceptable low risk scenario. IMO has adopted a guideline describing different risk assessment approaches (G7 Guidelines,...

The Working Group on the Introductions and Transfers of Marine Organisms (WGITMO) has contributed several major achievements to the ICES vision, including the first ICES Viewpoint on Biofouling and its source document, two Cooperative Research Reports, and numerous pub-lications related to ToRs, and the continued population of the AquaNIS database....

Refined baseline inventories of non-indigenous species (NIS) are set per European Union Member State (MS), in the context of the Marine Strategy Framework Directive (MSFD). The inventories are based on the initial assessment of the MSFD (2012) and the updated data of the European Alien Species Information Network, in collaboration with NIS experts...

The Arctic Limnocalanus macrurus is a prominent representative of large copepods which performs several essential functions in freshwater and marine ecosystems. Being a cold stenotherm species, its distribution is primarily confined to deeper water layers. Based on the long-term observations from one of the largest spatially confined natural popula...

In 2004, the United Nations (UN) General Assembly approved a Regular Process to report on the environmental, economic and social aspects of the world’s ocean. The Regular Process for Global Reporting and Assessment of the State of the Marine Environment, including Socioeconomic Aspects produced the first global integrated assessment of the marine e...

Ecosystem Overviews (EOs) are central products in the ICES approach to support Ecosystem Based Management, through providing the ecoregion context, identifying main pressures, asso-ciated human activities and impacts on ecosystem state. The WKEO3 explored and discussed both stakeholder/client and expert views on the development of the EOs, and asse...

Climate change in recent decades has been identified as a significant threat to natural environments and human wellbeing. This is because some of the contemporary changes to climate are abrupt and result in persistent changes in the state of natural systems; so called regime shifts (RS). This study aimed to detect and analyse the timing and strengt...

List of used time series, their original temporal resolution and spatial extent. Below potted history for each variable with identified regime shifts as broken lines. Number at the broken line reflects the statistical significance of the particular regime shift. (PDF)

A R script on how to depict a timing and relative strength of statistically significant RSs and the relatedness of time series within each system category (i.e. abiotic and biotic elements of atmospheric, terrestrial, bog, lake, river and marine systems) in terms of the timing of RSs. (PDF)

Incorporating ecosystem changes from non-indigenous species (NIS) is an important task of maritime spatial planning. Maritime spatial planning requires a framework that emphasises ecological functioning in a state of dynamic change, including changes to ecosystem services from functions introduced by new NIS. Adaptable modelling toolsets should be...

The BONUS symposium "Science delivery for sustainable use of the Baltic Sea living resources" held in Tallinn, Estonia, in October 2017 was an opportunity for the presentation and discussion of 107 papers that examined the state and dynamics of living resources of the Baltic Sea, and associated management challenges. The symposium included a half-d...

There is no sign of saturation in accumulation of alien species (AS) introductions worldwide, additionally the rate of spread for some species has also been shown to be increasing. However, the challenges of gathering information on AS are recognized. Recent developments in citizen science (CS) provide an opportunity to improve data flow and knowle...

The BONUS symposium "Science delivery for sustainable use of the Baltic Sea living resources" held in Tallinn, Estonia, in October 2017 was an opportunity for the presentation and discussion of 107 papers that examined the state and dynamics of living resources of the Baltic Sea, and associated management challenges. The symposium included a half-d...

The introduction of non-native species is an important element of global change in marine ecosystems. This phenomenon is considered to be among the main direct drivers of biodiversity change, exacerbated as it is by climate change, pollution, habitat loss and other human-induced disturbances. Some edible marine non-native species have been widely d...

The human-mediated introduction of marine non-indigenous species is a centuries- if not millennia-old phenomenon, but was only recently acknowledged as a potent driver of change in the sea. We provide a synopsis of key historical milestones for marine bioinvasions, including timelines of (a) discovery and understanding of the invasion process, focu...

HELCOM facts sheet (also available here http://www.helcom.fi/baltic-sea-trends/environment-fact-sheets/biodiversity/abundance-and-distribution-of-round-goby/) on the abundance, distribution and impacts of the invasive round goby (Neogobius melanostomus) in the Baltic region.

Coastal global oceans are expected to undergo drastic changes driven by climate change and increasing anthropogenic pressures in coming decades. Predicting specific future conditions and assessing the best management strategies to maintain ecosystem integrity and sustainable resource use are difficult, because of multiple interacting pressures, unc...

Historical marine ecology has shown that many exploited animal populations declined before their abundance was quantified by scientists. This situation applies for autumn-spawning herring (Clupea harengus) in the Baltic Sea. This stock used to be the dominant spawning group of herring in the early decades of the 1900s and supported several commerci...

Due to its unique characteristics with substantial drainage area and limited water exchange with the North Sea, considerable salinity gradient, permanent stratification as well as a combination of numerous, strong anthropogenic and climatic pressures the Baltic Sea environment is under constant stress. Considering the intensity of exploitation and...

Identification and quantification of pressure‐state links of biodiversity indicators is one of the major scientific challenges ahead. This task aimed at identifying and quantifying the pressure-state links of selected biodiversity indicators, their relevance and response to management measures. Relevant indicators have been selected based on their...

Predator–prey interactions are a primary structuring force in marine foodwebs and they play an important role in the dynamics of both marine fish populations and their prey. We investigated the individual and spatial patterns in the feeding of two dominant zooplanktivorous clupeids—herring Clupea harengus membras and sprat Sprattus sprattus—in the...

Invasive ecosystem engineers (IEE) are potentially one of the most influential types of biological invaders. They are expected to have extensive ecological impacts by altering the physical-chemical structure of ecosystems, thereby changing the rules of existence for a broad range of resident biota. To test the generality of this expectation, we use...

MERCES is producing a census of European marine key habitat maps, degraded habitat maps and investigating key habitat restoration potential.