Linking lipid dynamics with the reproductive cycle in Baltic cod Gadus morhua

Abstract

This study describes lipid composition and antioxidants of Baltic cod Gadus morhua L. during the reproductive cycle, and investigates whether they reflect its dominant prey and whether levels of fatty acids important for reproductive performance were low. Reasons for a shift in peak spawning time of Baltic cod from spring/early summer to midsummer since the early 1990s remain unresolved and may partly be diet related. This study demonstrated that a substantial amount of lipid was invested in cod ovarian development, and that lipid composition varied substantially with the reproductive cycle. Selective retention of the essential fatty acids docosahexaenoic acid (DHA) and arachidonic acid (ARA) in ovaries during maturation was evident, but despite mobilization from the liver, ARA levels were low in ovaries during late maturation and spawning. Astaxanthin and α-tocopherol accumulated in cod ovaries and decreased in late maturing and spawning fish, most likely due to their antioxidant protection activity. The fatty acid composition of cod liver reflected its clupeid prey. The ratio of 18:1n-9 to DHA was almost twice as high in sprat as in herring and indicated the ratio of sprat and herring in cod diet, while the level of 16:1n-7 and astaxanthin indicated the presence of the isopod Saduria entomon in cod diet. It is likely that food web alterations in the Baltic ecosystem related to environmental and hydrographic changes caused a decrease in ARA availability. Low ARA content coincides with cod ovarian development in the central Baltic Sea, and may be associated with the delay in spawning and affect egg and larval survival; however, this needs further verification in experimental studies.

Oxygen depletion in coastal seas and the effective spawning stock biomass of an exploited fish species

“…In addition, there are reasonable indications that the feeding conditions for adult eastern Baltic cod might have changed during the most recent decade [63,64]. Future work repeating laboratory experiments to assess potential changes in female age-dependent egg production and in the egg size relationship and to validate our findings under the present feeding regime would be useful.…”

Partitioning the Relative Importance of Phylogeny and Environmental Conditions on Phytoplankton Fatty Acids

“…Thus, our analysis is conservative in the estimation of total algal-derived EFA. The choice of these three conditionally essential LCEFA for broad analyses is not unprecedented [86,87]. Importantly, the strictly phytoplankton based estimates used here do not calculate total ecosystem seston LCEFA, which may also be stored in heterotophic protists [46,55,88].…”

Metabolic programming mediated by an essential fatty acid alters body composition and survival skills of a marine fish

“…EFAs that animals require for their own well-being are synthesized almost entirely by primary producers, principally phytoplankton and macroalgae in marine ecosystems, and they reach animals through a variety of food web linkages [28]. Changes in environmental conditions, such as upwelling, eutrophication, and ocean acidification can alter communities of primary producers, resulting in changes in the availability of EFAs to higher trophic levels which can alter the fatty acid composition of animals [29,30], the timing of reproduction [31], and the structure of communities on the scale of regime shifts [32]. The transgenerational link that metabolic programming establishes between ingestion of EFAs by adults and offspring fitness represents one specific pathway through which variations in EFA synthesis by primary producers might transmit through food webs to alter animal populations and communities.…”