Markus Vetemaa

The Estonian fisheries: from the Soviet system to ITQs and quota auctions

The development of the Estonian fisheries and fishing rights during the post-Soviet period is discussed. In order to deal with excessive fishing capacity, a part of the fishing rights, both volume quotas and gear-use rights, in all Estonian fisheries will be allocated each year through auctions while the remainder will be allocated on the basis of the history of the use of recent fishing rights. This was done for the first time in 2001. All fishing rights depreciate from year to year in a geometric fashion, by 10% yearly. The results of the first auctions discussed in the paper suggest that auctioning is a suitable method to manage common-pool resources such as fish stocks.

Alien species in a brackish water temperate ecosystem: annual-scale dynamics in response to environmental variability.

Alien species contribute to global change in all marine ecosystems. Environmental variability can affect species distribution and population sizes, and is therefore expected to influence alien species. In this study, we have investigated temporal variability of 11 alien species representing different trophic levels and ecological functions in two gulfs of the brackish Baltic Sea in relation to environmental change. Independent of the invasion time, organism group or the life-history stage, abundance and/or biomass of the investigated alien species was either stable or displayed abrupt increases over time. Timing in population shifts was species-specific and exhibited no generic patterns, indicating that the observed large shifts in environmental parameters have no uniform consequences to the alien biota. In general, the inter-annual dynamics of alien and native species was not largely different, though native species tended to exhibit more diverse variability patterns compared to the alien species. There were no key environmental factors that affected most of the alien species, instead, the effects varied among the studied gulfs and species. Non-indigenous species have caused prominent structural changes in invaded communities as a result of exponential increase in the most recent invasions, as well as increased densities of the already established alien species.

Early life migration patterns of Baltic Sea pike Esox lucius

This study investigated the movement patterns of Baltic Sea pike Esox lucius in Matsalu Bay, Estonia, using otolith microchemistry. Migration patterns of E. lucius were remarkably diverse, but distinct groups were evident. Of the E. lucius analysed (n = 28), 82% hatched in fresh water and 74% of them left this biotope during the first growth season.

From individuals to populations: impacts of environmental pollution on natural eelpout populations.

Investigating how individuals are affected by environmental pollution is relatively straightforward, for example through conducting field studies or laboratory toxicity tests. Exploring such effects at a population level is considerably more difficult. Nonetheless, the exploration of population-level effects is important as the outcomes may differ from those seen at the individual level. Eelpout (Zoarces viviparus L.) have been used for several years as a bioindicator for hazard substances in both the field and laboratory tests, and individual effects on reproduction have been reported. However, the influence of these effects at the population level remained unexplored. In this study, four Leslie matrix models were parameterized using data from non-polluted eelpout populations (Skagerrak, Baltic Proper, Gulf of Bothnia and Gulf of Finland). The four sites represent an environmental gradient in salinity. Furthermore, life-history data revealed differences between the sites with growth rate, fecundity, age at maturity and longevity being the most significant. The effect of pollution on natural eelpout populations was then simulated by combining the outputs from the Leslie matrices with data from laboratory and field studies exploring reproductive impairment in contaminated environments. Our results show that despite differences in life-history characteristics between sites, survival of early life stages (i.e. larvae and zero-year-old fish) was the most important factor affecting population growth and persistence for all sites. The range of change in survival of larvae necessary to change population dynamics (i.e. growth) and persistence is well within the range documented in recipient and experimental studies of chemicals and industrial waste waters. Overall, larval malformation resulting from environmental pollution can have large effects on natural populations, leading to population losses and possibly even extinction. This study hereby contributes valuable knowledge by extending individual-level effects of environmental contaminants to the population level.

By-Catch of Grey Seals (Halichoerus grypus) in Baltic Fisheries—A Bayesian Analysis of Interview Survey

Baltic seals are recovering after a population decline. The increasing seal stocks cause notable damage to fisheries in the Baltic Sea, with an unknown number of seals drowning in fishing gear every year. Thus, sustainable seal management requires updated knowledge of the by-catch of seals—the number of specimens that die in fishing gear. We analyse the by-catch of grey seals (Halichoerus grypus) in Finland, Sweden, and Estonia in 2012. We collect data with interviews (35 in Finland, 54 in Sweden, and 72 in Estonia) and analyse them with a hierarchical Bayesian model. The model accounts for variability in seal abundance, seal mortality and fishing effort in different sub-areas of the Baltic Sea and allows us to predict the by-catch in areas where interview data was not available. We provide a detailed description of the survey design and interview methods, and discuss different factors affecting fishermens motivation to report by-catch and how this may affect the results. Our analysis shows that the total yearly by-catch by trap and gill nets in Finland, Sweden and Estonia is, with 90% probability, more than 1240 but less than 2860; and the posterior median and mean of the total by-catch are 1550 and 1880 seals, respectively. Trap nets make about 88% of the total by-catch. However, results also indicate that in one of the sub-areas of this study, fishermen may have underreported their by-catch. Taking the possible underreporting into account the posterior mean of the total by-catch is between 2180 and 2380. The by-catch in our study area is likely to represent at least 90% of the total yearly grey seal by-catch in the Baltic Sea.

Competition for the fish - fish extraction from the Baltic Sea by humans, aquatic mammals and birds

Seals and fish-eating birds have increased in the Baltic Sea and there is concern that they compete with fisheries. Using data from around year 2010, we compare consumption of different fish specie ...

Food selection of Coregonus lavaretus in a brackish water ecosystem.

This study examined how variability in the abundance and biomass structure of benthic invertebrates affected the feeding choice of the whitefish Coregonus lavaretus on a hard bottom habitat of the brackish Baltic Sea. In general, crustaceans such as Idotea balthica and Gammarus spp. were preferred over molluscs. Although being the most numerous taxon in the invertebrate samples, Mytilus trossulus was the lowest ranking in C. lavaretus food preference. The availability of benthic invertebrate prey set the dietary range of fish but the selectivity largely described fish feeding within this range. There was no clear link between fish predation and the dominance structure of benthic invertebrate communities, suggesting that species composition, abundance and biomass of invertebrate species had no impact on the feeding selectivity of the fish. Thus, while fish predation may not affect the dominant species within a benthic community, due to strong selectivity fish may impose strong pressure on some rarer but highly preferred invertebrate prey species.

The Quota Auctions in Estonia and their Effect on the Trawler Fleet

The Estonian trawl fishery has been operating under an individual transferable quota (ITQ) system since 2001 when auctioning a part of the quota was also first implemented. This study analyzes the effect of quota auctions on the structure of the fleet and the performance of the system in managing excessive fishing capacity. The capacity of the Estonian trawling fleet is estimated for 2001 using Data Envelopment Analysis (DEA), and a 25% overcapacity was obtained. Higher capacity utilization compared to the rest of the fleet was observed for two types of large vessels that are economically more effective than smaller vessels and had historically obtained larger quota shares. The quota share of these types of vessels increased further as a result of the auction, and most of the auctioned quota was used by vessels with relatively high capacity utilization. An auction system in parallel with ITQs can be considered an effective method for increasing the allocation of fishing rights to the most effective enterprises and speeding the process of reducing excessive fleet capacity.

Invasion of round goby to the temperate salmonid streams in the Baltic Sea

Round goby Neogobius melanostomus, initially originating from the Ponto-Caspian region, has become one of the most successful invasive species in the Northern Hemisphere. During the last three decades, this invasive fish has established numerous populations both in Eurasia and North America (reviewed in Kornis et al. 2012). In Europe, this species has invaded lakes, large rivers and also various marine environments. In Northern America, round goby has started to spread from lakes to several estuaries, marshes and smaller tributaries (Poos et al. 2010; Kornis et al. 2012). High tolerance to various environmental factors, short generation time, opportunistic diet preferences and aggressive behaviour allows this species to colonize different biotopes (Corkum et al. 2004; Johnson et al. 2005; Brown and Stepien 2008; Kornis et al. 2014). Rapid invasion of round goby has proved to have impact on native fish populations in several invaded regions. Declines in abundance of some benthic fishes as stone loach Barbatula barbatula, bullhead Cottus gobio and white-finned gudgeon Romanogobio albipinnatus have been suggested in European freshwaters (Jurajda et al. 2005). In the Baltic Sea, the expansion of round goby has been suggested to affect flounder Platichthys flesus, eelpout Zoarces viviparus and native gobies (Balážová-L’avrincı́ková and Kovác 2007; Karlson et al. 2007). In North America, several percid and cottid species compete with round goby for food, territory and spawning grounds (Jude et al. 1995; Janssen and Jude 2001). Round goby invasion to the Baltic Sea was confirmed in 1990, when several fish were caught from Puck Bay in Poland (Skóra and Stolarski 1993). In the Estonian coastal sea, round goby was found in 2002, from Pärnu Bay in the Gulf of Riga (Shpilev and Ojaveer 2003). However, first rapidly growing population occurred during the mid-2000s in Muuga Bay near Tallinn, in the southern coast of the Gulf of Finland (Ojaveer 2006). During the 2010s, round goby dispersed widely along the southern coast of Gulf of Finland and became particularly abundant in several small bays east of Tallinn. Since 2011, the round gobies were found from six salmonid spawning streams along the North Estonian coast (Fig. 1). Fishes were caught during the national annual salmonid parr density survey, using backpack electrofishing gear. Study sites (two or three per stream) were located in rapid sections situated on the lower reaches of the streams which are accessible to anadromous salmonids. All sites were fished twice and the interval between sampling runs was at least 30 minutes. The abundance of salmonids and all other fish species were recorded, all caught fish were measured to the nearest mm (total length), kept in water buckets and released afterwards (except round gobies). Based on the maximum summer water temperatures, streams were classified as cool (13.1–17.0 C; three locations) or temperate (17.1–21.0 C; three locations) (Järvekülg 2001). The length of the streams varied between 25 and 85 km, catchment areas between 84–479 km and mean discharges in lower reaches between 0.5–4.0 m/s (Loopmann 1979) [Electronic Supplementary Material (ESM) Table S1]. All the studied sites were located in freshwater, and distances along a stream from the sea varied from 0.5 to 2.6 km. In three streams, where round Electronic supplementary material The online version of this article (doi:10.1007/s10228-016-0537-4) contains supplementary material, which is available to authorized users.

Variations in egg characteristics of ruffe Gymnocephalus cernua inhabiting brackish and freshwater environments

Egg characteristics of teleost fishes are affected by various abiotic and biotic factors. In order to reproduce successfully, freshwater fishes inhabiting brackish environments must alter their reproductive characteristics, including egg properties, to increased osmotic pressure. Ruffe Gymnocephalus cernua was used as a model species to compare egg characteristics between fish populations inhabiting brackish and freshwater environments. Fish from the brackish environment had larger eggs with higher energy content than the individuals originating from freshwater. In freshwater, eggs from the first batch were larger than from the second. Female size correlated positively with egg size in the brackish water population. In freshwater, this correlation was evident only with eggs from the first batch. Only a weak positive correlation was found between fish condition and egg size in females from the brackish water population. Egg size variation did not differ between sites, nor was it correlated with mean egg size or any other maternal traits within populations. These results indicate significant modifications in reproductive strategies between brackish and freshwater ruffe populations. Additionally, results show that at least in freshwater, the first batch of eggs is of the highest quality and therefore more important for reproduction.