Baltic cod endohelminths reflect recent ecological changes

2020 ◽  
Vol 94 ◽  
Author(s):  
A.C. Setyawan ◽  
H.M. Jensen ◽  
P.W. Kania ◽  
K. Buchmann
Keyword(s):  
Gadus Morhua ◽  
Comparative Investigation ◽  
Final Host ◽  
Oxygen Deficit ◽  
Marine Habitat ◽  
Ecological Changes ◽  
Third Stage ◽  
Contracaecum Osculatum ◽  
The Baltic ◽  
Baltic Cod

Abstract We suggest helminthological investigations of cod as a supplement to traditional biological and hydrographical methods for elucidation of ecological changes in the Baltic Sea. It is under discussion if oxygen deficit or seal abundance should explain the present critical situation of Baltic cod. A comparative investigation of endoparasitic helminths in Baltic cod (Gadus morhua), captured in the same marine habitat with an interval of 35 years (1983/2018) recorded 11 species of helminths comprising trematodes (Hemiurus luehei, Podocotyle atomon, Lepidapedon elongatum), nematodes (Contracaecum osculatum, Hysterothylacium aduncum, Capillaria gracilis, Cucullanus cirratus), cestodes (Bothriocephalus sp.) and acanthocephalans (Echinorhynchus gadi, Pomphorhynchus laevis, Corynosoma semerme). Significant prevalence and intensity increases were recorded for third-stage larvae of the nematode C. osculatum (liver location) and larvae of C. semerme (encapsulated in viscera). Both parasite species use grey seal as their final host, indicating the recent expansion of the Baltic seal population. A lower E. gadi intensity and an increased prevalence of L. elongatum of small cod (31–40 cm body length) suggest a lowered intake of amphipods (intermediate host) and elevated ingestion of polychaetes, respectively, but no significant changes were seen for other helminths.

scholarly journals Contracaecum osculatumand other anisakid nematodes in grey seals and cod in the Baltic Sea: molecular and ecological links

2017 ◽  
Vol 92 (1) ◽  
pp. 81-89 ◽  
Author(s):  
S. Zuo ◽  
P.W. Kania ◽  
F. Mehrdana ◽  
M.H. Marana ◽  
K. Buchmann
Keyword(s):  
Baltic Sea ◽  
Gadus Morhua ◽  
Final Host ◽  
The Baltic Sea ◽  
Fish Stocks ◽  
Pseudoterranova Decipiens ◽  
Contracaecum Osculatum ◽  
The Baltic ◽  
The Impact ◽  
Anisakid Nematodes

AbstractPopulations of grey seals (Halichoerus grypus), sprats (Sprattus sprattus) and cod (Gadus morhua) in the Baltic Sea are relatively stationary. The present work, applying classical and molecular helminthological techniques, documents that seals and cod also share a common parasite, the anisakid nematodeContracaecum osculatum, which uses seals as the final host and fish as transport hosts. Sequencing mitochondrial genes (COX1andCOX2) in adult worms from seals and third-stage larvae from livers of Baltic fish (sprats and cod), showed that all gene variants occur in both seals and fish. Other anisakid nematodesPseudoterranova decipiensandAnisakis simplexare also found in both seals and cod in the Baltic Sea, but at much lower rates. The Baltic grey seal population was left at a critically low level (comprising a few hundred individuals) during the latter part of the 20th century, but since the year 2000 a marked increase in the population has been observed, reaching more than 40,000 individuals at present. Ecological consequences of the increased seal abundance may result from increased predation on fish stocks, but recent evidence also points to the influence of elevated parasitism on fish performance.Contracaecum osculatumlarvae preferentially infect the liver of Baltic cod, considered a vital organ of the host. Whereas low prevalences and intensities in cod were reported during the 1980s and 1990s, the present study documents 100% prevalence and a mean intensity of above 80 worms per fish. Recent studies have also indicated the zoonotic potential ofC. osculatumlarvae in fish, following the consumption of raw or under-cooked fish. Therefore the present work discusses the impact of parasitism on the cod stock and the increasing risk for consumer health, and lists possible solutions for control.

scholarly journals Deoxygenation impacts on Baltic Sea cod: Dramatic declines in ecosystem services of an iconic keystone predator

AMBIO ◽  
2021 ◽  
Author(s):  
Alessandro Orio ◽  
Yvette Heimbrand ◽  
Karin Limburg
Keyword(s):  
Ecosystem Services ◽  
Baltic Sea ◽  
Gadus Morhua ◽  
Generalized Additive Model ◽  
Additive Model ◽  
Maximum Length ◽  
The Baltic Sea ◽  
Hypoxic Zone ◽  
The Baltic ◽  
Baltic Cod

AbstractThe intensified expansion of the Baltic Sea’s hypoxic zone has been proposed as one reason for the current poor status of cod (Gadus morhua) in the Baltic Sea, with repercussions throughout the food web and on ecosystem services. We examined the links between increased hypoxic areas and the decline in maximum length of Baltic cod, a demographic proxy for services generation. We analysed the effect of different predictors on maximum length of Baltic cod during 1978–2014 using a generalized additive model. The extent of minimally suitable areas for cod (oxygen concentration ≥ 1 ml l−1) is the most important predictor of decreased cod maximum length. We also show, with simulations, the potential for Baltic cod to increase its maximum length if hypoxic areal extent is reduced to levels comparable to the beginning of the 1990s. We discuss our findings in relation to ecosystem services affected by the decrease of cod maximum length.

scholarly journals Factors affecting rule compliance with mesh size regulations in the Baltic cod trawl fishery

2007 ◽  
Vol 64 (8) ◽  
pp. 1603-1606 ◽  
Author(s):  
Petri Suuronen ◽  
Vesa Tschernij ◽  
Pekka Jounela ◽  
Daniel Valentinsson ◽  
P-O. Larsson
Keyword(s):  
Gadus Morhua ◽  
Management Practice ◽  
Mesh Size ◽  
Factors Affecting ◽  
Trawl Fishery ◽  
Management Measures ◽  
Gradual Introduction ◽  
Minimum Landing Size ◽  
The Baltic ◽  
Baltic Cod

Abstract Suuronen, P., Tschernij, V., Jounela, P., Valentinsson, D., and Larsson, P-O. 2007. Factors affecting rule compiance with mesh size regulations in the Baltic cod trawl fishery. – ICES Journal of Marine Science, 64: 1603–1606. In this study, we evaluate the efficiency and applicability of a series of gear-based management measures, enforced since 1990, whose purpose was to improve size selectivity in the trawl fishery for Baltic cod (Gadus morhua). In general, our study revealed that these measures had no marked effect on the capture and discard of young cod. Legal and illegal manipulation of selective codends was widespread. The adoption of a codend design that offered a modest increase in selectivity, but had a good match with the legislated minimum landing size (MLS), led to greater compliance, demonstrating that a mismatch between MLS and selectivity should be avoided. It was also obvious that, generally, the fishing industry did not tolerate large short-term losses. Our evaluation is that overly ambitious rules will be circumvented, and frequent and incoherent changes in the regulations represent bad management practice. A gradual introduction of restrictions and participation by fishers in the decision-making process will increase compliance.

scholarly journals Post-smolt survival of Baltic salmon in context to changing environmental conditions and predators

2016 ◽  
Vol 74 (5) ◽  
pp. 1344-1355 ◽  
Author(s):  
Kevin D. Friedland ◽  
Johan Dannewitz ◽  
Atso Romakkaniemi ◽  
Stefan Palm ◽  
Henni Pulkkinen ◽  
...  
Keyword(s):  
Environmental Conditions ◽  
Coastal Waters ◽  
Gadus Morhua ◽  
Environmental Parameters ◽  
Predation Pressure ◽  
First Year ◽  
Central Basin ◽  
The Baltic ◽  
Latitudinal Range ◽  
Baltic Cod

The survival of Baltic salmon Salmo salar during the first year at sea (post-smolt stage) has declined since the beginning of the 1990s. In this analysis, we complement previous studies on possible causes of this decline by considering a suite of environmental parameters, potential change in predation pressure, and post-smolt growth. Marine survival estimates were found to be negatively correlated with temperature, indicating that warming conditions have not favoured survival. Survival was also found to be positively correlated with dissolved oxygen levels and regionally related to shifts in salinity. These relationships were further studied in context to the potential predation on post-smolts by one of the main piscivores in the Baltic, Eastern Baltic cod (Gadus morhua callarias). Concomitant with changes in environmental conditions, Baltic cod has changed its latitudinal range, moving northward in the Baltic, possibly in response to warming conditions. These changes lead us to hypothesize that predation pressure on salmon may have increased in recent years as cod has now occupied habitats used by salmon post-smolts during their southward feeding migrations. This predation may have been intensified as a result of anoxic conditions in the central basin by concentrating predation interactions in coastal waters and/or the upper water column typically occupied by salmon post-smolts. Indicators of post-smolt growth were applied to test the alternate hypothesis that mortality is growth-mediated; these indicators lacked a time series trend, which supports the contention that shifting predation pressure rather than feeding opportunities is responsible for the decline in post-smolt survival in Baltic salmon.

Early embryonic cleavage pattern, hatching success, and egg-lipid fatty acid composition: comparison between two cod (Gadus morhua) stocks

1997 ◽  
Vol 54 (10) ◽  
pp. 2410-2416 ◽  
Author(s):  
J Pickova ◽  
P C Dutta ◽  
P -O Larsson ◽  
A Kiessling
Keyword(s):  
Gadus Morhua ◽  
Hatching Success ◽  
Hatching Rate ◽  
Cleavage Pattern ◽  
Egg Viability ◽  
Lipid Fatty Acid ◽  
Embryonic Cleavage ◽  
The Baltic ◽  
Lipid Fatty Acid Composition ◽  
Baltic Cod

Baltic cod (Gadus morhua), from a brackish environment, were compared with oceanic (Skagerrak) cod in terms of early embryonic cleavage pattern, hatching success, and egg-lipid fatty acid composition. The influence of diet on these variables was investigated by analysing eggs from the Baltic stock, caught during three successive years and given controlled food for 24, 7, and 2 months, respectively, before the experiment commenced. Skagerrak cod eggs contained twice as much arachidonic acid (AA) in the phospholipid (PL) fraction as eggs from the Baltic cod, regardless of the length of time the Baltic cod had been kept in captivity and fed a control diet. Correlation between hatching rate and docosahexaenoic (DHA; 22:6n-3)/ eicosapentaenoic acid (EPA; 20:5n-3) ratio was significant (r2 = 0.56) as well as hatching rate and AA content of the PL fraction (r2 = 0.61). Symmetry during development, which was correlated to egg viability, was higher for eggs from Skagerrak than those from the Baltic stock. We suggest that AA content and DHA/EPA ratio of the PL fraction are important factors influencing egg viability and possibly also egg symmetry.\b Further, it appears that the factor(s) influencing the composition of the PL fraction is mostly related to stock rather than to diet.

scholarly journals Review of western Baltic cod (Gadus morhua) recruitment dynamics

2011 ◽  
Vol 68 (7) ◽  
pp. 1459-1471 ◽  
Author(s):  
Karin Hüssy
Keyword(s):  
Gadus Morhua ◽  
Specific Pattern ◽  
Genetic Stock ◽  
Neutral Buoyancy ◽  
Natal Homing ◽  
Spawning Areas ◽  
Arkona Basin ◽  
The Baltic ◽  
East West ◽  
Baltic Cod

Abstract Hüssy, K. 2011. Review of western Baltic cod (Gadus morhua) recruitment dynamics. – ICES Journal of Marine Science, 68: 1459–1471. Important processes in the recruitment dynamics of western Baltic cod (Gadus morhua) are identified. Spawning areas are in the deep, saline waters below 20–40 m, depending on area topography. Spatial distribution remains relatively stable over time. Peak spawning shows an area-specific pattern, with progressively later spawning towards the east. Genetic stock structure and tagging indicate some degree of natal homing for spawning. The highly variable hydrodynamic conditions and the fact that cod eggs float in the water column cause their entrainment by currents, and their destination is determined by the prevailing winds and currents. Drift is almost exclusively to the east, but the magnitude and its impact on the structure of the affected stocks (Kattegat, western Baltic, and eastern Baltic) remains unresolved. Salinity limits the east–west exchange of eggs as a consequence of the stocks' differential requirement for neutral buoyancy. Superimposed on this, oxygen content and temperature have a significant effect on fertilization, egg/larva development, and survival. Within the Baltic Sea ecosystem, mixing of stocks may be anticipated and is particularly pronounced in the Arkona Basin because of its use for spawning by both western and eastern stocks, the advection of early life stages from the west and immigration/emigration from the east.

Sign in / Sign up

Export Citation Format

Share Document