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In Nederland wordt veel ecologisch onderzoek gedaan naar vissen, vaak gericht op het migratiegedrag en de belemmeringen die vissen tegenkomen wanneer ze tussen de verschillende leefgebieden migreren. Als vissen worden voorzien van zenders of merkjes staat het welzijn hierbij centraal.

Wat is de invloed van licht op vissen? Dat proberen onderzoekers van de Universiteit Leiden en hogeschool Van Hall Larenstein uit te zoeken. Bij het gemaal van Roptasyl wordt een proef gedaan.

In Nederland wordt veel ecologisch onderzoek gedaan naar vissen, vaak gericht op het migratiegedrag en de belemmeringen die vissen tegenkomen wanneer ze tussen de verschillende leefgebieden migreren. Als vissen worden voorzien van zenders of merkjes staat het welzijn hierbij centraal.

Het is een reis van zo'n 6.000 kilometer, maar vooral op de eerste kilometers komen ze allerlei obstakels tegen: de palingen die van Fryslân naar de Sargassozee bij Bermuda willen.

Het gaat helaas niet goed met de visstand van de Waddenzee. Er zwemmen minder vissen en ze worden steeds kleiner. Vooral trekvissen – die zowel zout als zoet water nodig hebben en vrij tussen beide moeten kunnen migreren – hebben het zwaar. Veel vissoorten worden op dit moment in hun trek gehinderd.

Dit voorjaar staat in het teken van een groot onderzoek naar vismigratie, omdat het slecht gaat met de visstand, mede door de vele blokkades van dijken, dammen en wegen. Het project 'Vissen voor Verbinding' waarbij tal van organisaties betrokken zijn, waaronder hogeschool Van Hall Larenstein, moet leiden tot een betere verbinding waardoor trekvissen kunnen migreren tussen Waddenzee, Lauwersmeer en achterliggende wateren zoals Eelderdiep en Peizerdiep. In april 2021 werden 140 jonge forellen uitgezet in het Peizerdiep. Voor het eerst zijn de vissen voorzien van zenders.

Dit voorjaar staat in het teken van een groot onderzoek naar vismigratie, omdat het slecht gaat met de visstand, mede door de vele blokkades van dijken, dammen en wegen. Het project 'Vissen voor Verbinding' waarbij tal van organisaties betrokken zijn, waaronder hogeschool Van Hall Larenstein, moet leiden tot een betere verbinding waardoor trekvissen kunnen migreren tussen Waddenzee, Lauwersmeer en achterliggende wateren zoals Eelderdiep en Peizerdiep. In april 2021 werden 140 jonge forellen uitgezet in het Peizerdiep. Voor het eerst zijn de vissen voorzien van zenders.

De doelstellingen van deze rapportage in opdracht van RWS zijn: 1) een overzicht maken van de belangrijkste kennis- en beheersvragen m.b.t. vismigratie en estuarien habitat in zoet-zoutovergangen langs de Nederlandse kust en specifiek de Kier; 2) een overzicht maken van lopend en gepland vismonitoring en -onderzoek in en rond de delta; 3) een verkenning uitvoeren van wetenschappelijke kennis m.b.t. vismigratie en habitatgebruik bij zoet-zoutovergangen en te bepalen welke kennishiaten er nog zijn; 4) identificeren van de wetenschappelijk meest relevante onderzoeksrichtingen en -methoden die voorzien in de kennisbehoefte voor beheer; 5) aanbevelingen voor inrichting van een platform t.b.v. landelijke coördinatie en afstemming van de verschillende vismigratie-onderzoeken en -projecten rondom zoet-zout overgangen.

Pulse trawl fisheries involve the use of electrical pulses to immobilize (cramp) target species and make them available for capture. A major concern related to pulse trawl fisheries is the passing pulse trawl causing direct, mass mortalities among benthic organisms, resulting in a ‘graveyard’ in the wake of a pulse trawler. This has never been investigated in situ and the current pilot study therefore aimed to develop a method for in situ assessments and to perform a first assessment. A pulse trawler equipped with double rigs made pulse trawl tracks specific for the current experiment. Within 15 to 30 minutes after passage of the pulse trawler, one of its trawl tracks was sampled with a shrimp trawler by a 10 minute tow with a small mesh shrimp beam trawl while the other, similar shrimp trawl was deployed outside the pulse trawl track to obtain control samples. The experiment consisted of two pulse trawl track treatments: a complete pulse trawl and a pulse trawl with its netting and ground rope removed to minimize its mechanical impact. This allowed for isolating electrical from mechanical impacts. In total two paired samples of treatments and controls were obtained per pulse trawl track treatment. The condition of three fish species and three species of invertebrates was assessed. Fish species included plaice (Pleuronectus platessa), dab (Limanda limanda) and solenette (Buglossidium luteum). Invertebrate species included flying crab (Liocarcinus holsatus), hermit crabs (Paguroidea spp.) and brittle stars (Ophiuroidea spp.). Direct survival ranged from 91-100% among treatments for the fish and 88-100% for the invertebrates. No significant differences in direct survival were detected between the two treatments and their respective controls for any of the species. Underwater video observations confirmed deployment of the sampling trawl inside the pulse trawl tracks, although part of swept area was outside the pulse trawl tracks. However, also when correcting the observed direct mortality for this, no differences between treatments and controls were detected. We conclude that with the right equipment, skilled skippers and a calm sea, it is possible to collect biota samples from a track recently trawled by a pulse trawler. However, it is very difficult to sample exclusively from a pulse trawl track; it is inevitable that part of the area swept by a sampling tow lies outside the pulse trawl track aimed for. Despite these limitations, any direct mass mortality caused by a passing pulse trawler would have been recorded in the current study, not only for the systematically observed species but also for other species in the samples. Our study thus did not find any evidence of direct mortality among plaice, dab, solenette, flying crab and brittle stars.

Het gaat helaas niet goed met de visstand van de Waddenzee. Er zwemmen minder vissen en ze worden steeds kleiner. Vooral trekvissen – die zowel zout als zoet water nodig hebben en vrij tussen beide moeten kunnen migreren – hebben het zwaar. Veel vissoorten worden op dit moment in hun trek gehinderd.

Viviparity, a live-bearing mode of reproduction, has evolved over 100 times independently in vertebrate animals. Despite its frequent evolution, viviparity has a number of hypothesised disadvantages compared to the ancestral mode of reproduction, oviparity (egg-laying). One of these disadvantages is a reduction in locomotor performance during pregnancy, the period of internal development of the embryos. Adaptations to a live-bearing reproductive mode could have evolved to reduce these locomotor costs. In this thesis, I aim to find whether matrotrophy, post-fertilization nutrient provisioning (e.g. through a placental structure), and superfetation, the presence of multiple broods of different developmental stages, reduce the locomotor performance decline during pregnancy in the Poeciliidae, live-bearing fishes. In Chapter 2, we review the literature on the effects of pregnancy on morphology, performance and fitness. The biomechanics of each mode of locomotion (walking, swimming or flying) are distinct, and are affected differently by the added mass and volume of pregnancy. Furthermore, we list the possible adaptations that have evolved to reduce the locomotor costs of pregnancy, and divide them into three different categories: adaptations that reduce the locomotor costs of live-bearing, adaptations with which the locomotor costs of live-bearing are avoided, and adaptations to the life history of the animal. Lastly, we discuss hiatuses in the literature and experimental procedures to quantify the hypothesised benefit of adaptations. In Chapter 3, we compare the morphological changes during pregnancy in two closely-related species of live-bearing fish: Poeciliopsis turneri and Poeciliopsis gracilis. These species mainly differ in their mode of nutrient provisioning: P. gracilis is lecithotrophic and P. turneri is an extensive matrotroph. We tracked the morphological changes in 3D using a non-invasive method that creates three-dimensional body models. We find that P. turneri is more slender during the early stages of pregnancy, but increase in size more rapidly. This is in line with the locomotor costs hypothesis, which predicts that matrotrophic fish are more slender during the early stages of pregnancy, but that the difference between the body shapes of lecithotrophic and matrotrophic fish diminishes as pregnancy progresses. Our results indicate that matrotrophy could indeed provide a morphological advantage during pregnancy. Fast-start performance, a manoeuvre fish deploy to escape predatory strikes, is important for individual survival. In Chapter 4, we use state-of-the-art biomechanical methods to, for the first time, quantify this manoeuvre in three-dimensional space in adult fish (Heterandria formosa). We show that fish can orient their escapes in up- and downwards direction, and that this is correlated with a change in pitch angle of the body. Changes in roll angle of the body were not correlated with orientation of the fish. We furthermore demonstrate that stage 1 of the fast start, often described as a preparatory stage, can already contribute to propulsion. The results from Chapter 4 indicate that three-dimensional measurements of fast-start manoeuvres provide novel insights that were often overlooked. Measuring fast starts in three-dimensional space is relevant in determining the adverse effects of pregnancy on locomotor performance. We did this by comparing three species of live-bearing fish: P. turneri, H. formosa and Phalloptychus januarius. In Chapter 5, we show that pregnancy-induced changes in abdominal width are correlated with a reduction in performance in the horizontal plane (maximal horizontal speed, change in yaw angle), but less so in the vertical plane (maximal vertical speed, change in pitch angle). Furthermore, we demonstrate that an increase in abdominal width is correlated with a decrease in abdominal curvature and, for some species, in a decrease in maximal curvature rate in the abdomen. Lastly, we show that the pregnancy-induced morphological changes depend on the level of superfetation: species with a high level of superfetation experience higher frequency, but smaller amplitude changes in the shape of the abdomen. Whether superfetation actually results in a more slender body shape, as predicted by the locomotor costs hypothesis, depends on the level of reproductive investment. In this thesis, I show that pregnancy induces changes in morphology which comes with a cost in fast-start performance. Both matrotrophy and superfetation affect how body shape changes due to pregnancy, but whether the latter provides beneficial changes depends on the level of reproductive investment. Furthermore, I reveal that fast starts can have a substantial three-dimensional component which is relevant both to biomechanicists that aim to understand the physical and physiological mechanisms underlying this manoeuvre and to evolutionary biologists that strive to answer performance-related questions.

Het Ministerie van Economische Zaken wil komen tot wetenschappelijk onderbouwd duurzaam beheer van snoekbaars, baars, blankvoorn en brasem in het IJsselmeer en Markermeer. Voor alle vier bestanden is de beleidsdoelstelling voor visseizoen 2017/2018 geformuleerd in het document “Toekomstbeeld visstand IJsselmeer/Markermeer – synthesedocument’. Hierin wordt in ieder geval gestreefd naar ‘een evenwichtiger lengte-opbouw van de bestanden met meer grotere exemplaren en een groter aantal jaarklassen’, als ook ‘een toename van de (paai)bestanden’. Voor het behalen van deze beleidsdoelstellingen zijn inspanningsadviezen gevraagd over de staandwantvisserij en de zegenvisserij, gecombineerd voor het IJsselmeer en Markermeer.

Climate change, specifically temperature, affects the distribution and densities of species in marine and terrestrial ecosystems. Here, we looked at the effect of temperature during winter and spawning period on latitudinal range shifts and changes in abundance of two non-commercial North Sea fish species, solenette ( Buglossidium luteum ) and scaldfish ( Arnoglossus laterna ). Both species have increased in abundance and moved to the north since the late 1980s, coinciding with a series of mild winters. In 1996, following a very cold winter, the abundance of both species temporarily decreased as they retracted to the south. The shift in temperature affected adult habitat conditions, allowing them to immigrate into new areas where they subsequently reproduced successfully. We can conclude this because recruitment improved following the increase in abundance. The recruitment relates significantly to the higher adult stock and higher temperatures. The predictions of higher average temperatures and milder winters in the North Sea make it likely that these species will increase further in abundance and move northward. The observed increase in abundance of these small flatfish species will affect the North Sea food web and therefore commercial species, e.g. plaice, by predation on juveniles and competition for benthic food resources.

Rijnsdorp, A. D., Peck, M. A., Engelhard, G. H., Möllmann, C., and Pinnegar, J. K. 2009. Resolving the effect of climate change on fish populations. – ICES Journal of Marine Science, 66: 1570–1583. This paper develops a framework for the study of climate on fish populations based on first principles of physiology, ecology, and available observations. Environmental variables and oceanographic features that are relevant to fish and that are likely to be affected by climate change are reviewed. Working hypotheses are derived from the differences in the expected response of different species groups. A review of published data on Northeast Atlantic fish species representing different biogeographic affinities, habitats, and body size lends support to the hypothesis that global warming results in a shift in abundance and distribution (in patterns of occurrence with latitude and depth) of fish species. Pelagic species exhibit clear changes in seasonal migration patterns related to climate-induced changes in zooplankton productivity. Lusitanian species have increased in recent decades (sprat, anchovy, and horse mackerel), especially at the northern limit of their distribution areas, while Boreal species decreased at the southern limit of their distribution range (cod and plaice), but increased at the northern limit (cod). Although the underlying mechanisms remain uncertain, available evidence suggests climate-related changes in recruitment success to be the key process, stemming from either higher production or survival in the pelagic egg or larval stage, or owing to changes in the quality/quantity of nursery habitats.

Het afgelopen decennium zijn de Nederlandse rivieren in hoog tempo gekoloniseerd door vier Ponto-Kaspische grondelsoorten, namelijk de marmergrondel (Proterorhinus semilunaris), zwartbekgrondel (Neogobius melanostomus), Kesslers grondel (Ponticola kessleri) en Pontische stroomgrondel (Neogobius fluviatilis). Deze uitheemse grondels zijn invasieve vissen met een bodemgebonden levenswijze en kunnen plaatselijk in hoge dichtheden voorkomen. Hoewel de verspreidingpatronen van invasieve grondels in Nederland tot op heden grofweg bekend zijn, bestaat geen duidelijk inzicht in de verspreidingprocessen en dichtheden van de grondels in verschillende watertypen, hun (ecologische) effecten en kansrijke mogelijkheden om ongewenste effecten te beperken.

This book contains 34 chapters on nutrition physiology and presents scientific research in modelling nutrient digestion and utilization in domestic animals, including cattle, sheep, pigs, poultry and fishes. It is divided into 6 parts that cover fermentation, absorption and passage; growth and development; mineral metabolism; methodology and model development; environmental impacts and animal production and feed evaluation models. Deterministic, stochastic, empirical and mechanistic modelling approaches are also described. This book will be of significant interest to researchers and students of animal science, especially those concerned with nutrition modelling.

This book contains 34 chapters on nutrition physiology and presents scientific research in modelling nutrient digestion and utilization in domestic animals, including cattle, sheep, pigs, poultry and fishes. It is divided into 6 parts that cover fermentation, absorption and passage; growth and development; mineral metabolism; methodology and model development; environmental impacts and animal production and feed evaluation models. Deterministic, stochastic, empirical and mechanistic modelling approaches are also described. This book will be of significant interest to researchers and students of animal science, especially those concerned with nutrition modelling.

We first examined the uptake kinetics of Cd and Zn in the juvenile marine black sea bream (Acanthopagrus schlegeli) over a wide range of ambient Cd and Zn concentrations, and the relationships with metal accumulation (uptake rate and amount of nonexchangeable surface binding) were established for different fish tissues. Both Cd and Zn accumulation in the body increased linearly with exposure time after the initial metal surface binding. The dissolved Cd and Zn uptake rate constants were 2.64 and 6.50 L/kg/d, respectively, and the kinetics followed a first-order process. No evidence of biphasic transport was found, in contrast to the situation in freshwater fish. Viscera were the most important sites of metal uptake, and gills were the second most important sites. The black sea breams were then acclimated at different Cd or Zn concentrations from either waterborne or dietary source for one week, and the alteration of metal uptake kinetics or subcellular distribution and metallothionein (MT) induction were further quantified. The Cd body burden was enhanced up to 8.6- and 49-fold after waterborne and dietary Cd pre-exposure, respectively. Cadmium pre-exposure also altered the tissue-specific subcellular Cd distribution and significantly elevated tissue MT levels. In contrast, the black sea breams were able to regulate Zn accumulation, and waterborne or dietary Zn pre-exposure had only weak influences on Zn body burden and redistribution. Both Cd and Zn pre-exposures enhanced the metal uptake rate constants, whereas the nonexchangeable surface bindings were less impacted by these pre-exposures. We demonstrated a positive relationship between the Cd uptake rate and Cd or MT concentration in the fish. Pre-exposure to metals may substantially modify the kinetics of metal uptake.

In de Waddenzee zwemt een flink aantal vissoorten, maar dat wil niet zeggen dat het goed gaat met alle soorten. Samen met andere landen wordt geprobeerd te achterhalen waar de knelpunten zitten. Artikel geschreven door Paddy Walker, lector 'Kust en zee' bij Van Hall Larenstein in Leeuwarden.

Met de visstand van de Waddenzee is het slecht gesteld. Keihard is de kritiek van de Waddenvereniging: kennis ontbreekt en beleid blijft achterwege. In het artikel wordt Jeroen Huisman, docent aan Van Hall Larenstein, aan het woord gelaten.

In het kader van het project 'Ruim baan voor vissen 2' worden windes in het Peizerdiep voorzien van een zendertje om hun migratie te kunnen volgen. Aan het woord o.a. Jeroen Huisman, van het lectoraat 'Coastal and Marine Management and Conservation' van hogeschool Van Hall Larenstein.

De afgelopen 55 jaar is maar liefst negentig procent van de vis in de Waddenzee verdwenen. Waar zijn al die vissen gebleven? Om daarachter te komen is een groot onderzoek gestart en daarin moeten de vissen zelf het antwoord geven middels een zendertje dat hun locatie doorgeeft. Dit project maakt onderdeel uit van het project 'Ruim baan voor vissen 2' waar o.a. hogeschool Van Hall Larenstein bij betrokken is.

Met de visstand van de Waddenzee is het slecht gesteld. Keihard is de kritiek van de Waddenvereniging: kennis ontbreekt en beleid blijft achterwege. In het artikel wordt Jeroen Huisman, docent aan Van Hall Larenstein, aan het woord gelaten.

In de Waddenzee zwemt een flink aantal vissoorten, maar dat wil niet zeggen dat het goed gaat met alle soorten. Samen met andere landen wordt geprobeerd te achterhalen waar de knelpunten zitten. Artikel geschreven door Paddy Walker, lector 'Kust en zee' bij Van Hall Larenstein in Leeuwarden.