Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The Bay of Biscay, a good feeding environment for the larvae of anchovy, sardine and horse-mackerel

12.09.2008
A PhD thesis, defended at the University of the Basque Country, analyses the nutritional state of the larvae of anchovy, sardine and horse-mackerel, as well as their growth strategy. Its conclusions point to the Bay of Biscay being a good feeding ground for these species.

The anchovy, sardine and horse-mackerel are three species of great commercial interest to the Basque fishing fleet. However, all three have suffered considerable fluctuations in their catches over the last few decades, reaching all time lows at times. This variability in the catches, due in part to the high mortality rate of their larvae, with lower numbers reaching adulthood, generates great uncertainty when trying to plan good fisheries management.

Predation and food availability are the most important factors in the mortality of larvae and this is why they were the target of the PhD thesis that Ms Estibaliz Díaz Silvestre has defended at the University of the Basque Country (UPV/EHU): Condition and biochemical composition of three pelagic larvae in the Bay of Biscay. The research work was led by doctors Fernando Villate Guinea and Jesus Mari Txurruka Argarate of the Department of Plant Biology and Ecology at the University’s Faculty of Science and Technology. Dr. Díaz is a Biology graduate and currently working as a researcher at the AZTI-Tecnalia Foundation. Apart from this foundation, participating in the project within which the PhD thesis was based, was the CSIC of Barcelona, the Instituto Español de Oceanografía and the University of Vigo.

This research was based on the general hypothesis that better-fed larvae grow better and, thereby, undergo less risk of depredation and lack of nutrition. However, the metabolism of the larvae has to reach a balance between the energy devoted to growth and fleeing predators, on the one hand and, on the other, creating reserves of energy to withstand periods when they are needed, such as winter or during metamorphosis. Thus, Dr. Díaz studied, on the one hand, the nutritional environment and state of the larvae during the period of reproduction of the anchovy, sardine and horse-mackerel and, on the other, different strategies of growth adopted by each species in order to achieve this balance.

Well fed larvae

Dr. Díaz’s research was undertaken using six sample surveys (May, June and July 2000, and April, May and June 2001) and carried out off the coast of the City of Donostia-San Sebastian. Her first objective was to describe the nutritional environment inhabited by the larvae of the fishes during the period of maximum reproduction and, to this end, based on the biochemical composition of the seston (the particles on which the larvae feed). The initial hypothesis was that the nutritional environment along the Basque coast was sufficiently rich to enable the survival of the larvae of the anchovy, sardine and horse-mackerel, and the results from the period studied confirmed this.

Apart from the quantity and quality of food available to the fish larvae, Dr. Díaz has analysed their nutritional state. To this end, the analysis was based on the RNA/DNA index, taking into consideration the quantity of RNA present in cells in comparison to DNA. Her conclusion was that the nutritional condition of the three species is good, coinciding with previous studies, observing scant presence of larvae with signs of starvation.

Two different strategies for growth

From the start of the development stage of the anchovy, sardine and horse-mackerel, proteins are their major food component, followed by lipids and carbohydrates. Nevertheless, the temporary patterns of accumulation of these substances are different in the case common to the first two species, both belonging to clupeids, from the horse-mackerel: with the first two, the percentages of proteins and RNA growth reaching a threshold, while the percentage of lipids and carbohydrates drop reaching a specific minimum for each species (anchovy or sardine). On the other hand, the horse-mackerel shows highly variable percentages during the first stages of growths, that stabilise at later stages, and reach values similar to those of other species.

According to Dr. Díaz, these differences in the biochemical composition of the species could be due to the different growth strategies adopted by each. The anchovy and the sardine, being larvae with anguiliform morphology (elongated), need to grow more rapidly at early stages than the horse-mackerel and, thus, their metabolism is given over to accumulating proteins to form muscle. The larva of the horse-mackerel, on the other hand, is like a tadpole; it swims better than a clupeid larva of the same size — thus enabling it to flee predators more easily — and it has a bigger mouth to capture more and bigger prey.

The conclusions of this PhD defended at the UPV/EHU state that, although initially both groups accumulate nutrients in different proportions, both anchovy and sardine and the horse-mackerel finally coincide with the same the biochemical composition. Dr. Díaz believes that if other species of larvae are studies, these proportions will not differ much from those found in the study, as the patterns of growth and development follow the rigorous rules dictated by natural selection and the biochemical composition of the larvae only means a variation of these patterns.

Dr. Díaz also states that it would be advisable to measure the changes in the biochemical composition of the anchovy, sardine and horse-mackerel in other locations and under different environmental conditions, in order to confirm or otherwise the existence of two different strategies of growth for the two morphological groups studied.

Lucía Álvarez | alfa
Further information:
http://www.elhuyar.com
http://www.basqueresearch.com/berria_irakurri.asp?Berri_Kod=1865&hizk=I

More articles from Life Sciences:

nachricht Fine organic particles in the atmosphere are more often solid glass beads than liquid oil droplets
21.04.2017 | Max-Planck-Institut für Chemie

nachricht Study overturns seminal research about the developing nervous system
21.04.2017 | University of California - Los Angeles Health Sciences

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

Im Focus: Quantum-physical Model System

Computer-assisted methods aid Heidelberg physicists in reproducing experiment with ultracold atoms

Two researchers at Heidelberg University have developed a model system that enables a better understanding of the processes in a quantum-physical experiment...

Im Focus: Glacier bacteria’s contribution to carbon cycling

Glaciers might seem rather inhospitable environments. However, they are home to a diverse and vibrant microbial community. It’s becoming increasingly clear that they play a bigger role in the carbon cycle than previously thought.

A new study, now published in the journal Nature Geoscience, shows how microbial communities in melting glaciers contribute to the Earth’s carbon cycle, a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

New quantum liquid crystals may play role in future of computers

21.04.2017 | Physics and Astronomy

A promising target for kidney fibrosis

21.04.2017 | Health and Medicine

Light rays from a supernova bent by the curvature of space-time around a galaxy

21.04.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>