Showing posts with label JOURNAL PAPERS. Show all posts
Showing posts with label JOURNAL PAPERS. Show all posts

Wednesday, April 6, 2016

A Reappraisal of Reproduction in Anadromous Alewives: Determinate versus Indeterminate Fecundity, Batch Size, and Batch Number - Transactions of the American Fisheries Society - Volume 144, Issue 6

2:42 PM – by

Environmentally Friendly Practices and Perceptions in Aquaculture: A Sectoral Case-study from a Mediterranean-based Industry - Reviews in Fisheries Science & Aquaculture - Volume 24, Issue 2

2:40 PM – by

Wednesday, August 26, 2015

Maternal versus environmental constraints on the oocyte size of a marine pelagophil fish - Online First - Springer

10:19 AM – by
Maternal versus environmental constraints on the oocyte size of a marine pelagophil fish

Abstract


We investigated maternal body size and environmental effects on the oocyte size of the Atlantic sardine, Sardina pilchardus, a marine pelagophil, using a novel, oocyte stage-specific approach which takes into account the spawning lag. In particular, we focused on anatomical constraints imposed by the maternal body cavity to the growth of the ovary and its oocytes during the course of vitellogenesis (VIT) and oocyte maturation (OM). We analyzed variability in oocyte size in VIT and OM ovaries as a factor of maternal size, ambient temperature (SST) and preservation medium (formalin vs. ethanol) using the spawning lag of recent and imminent spawners, respectively, as a covariate. We showed that oocyte size correlates with maternal size in OM ovaries but not in VIT ovaries. More specifically, 10 cm difference in maternal body length corresponds to 0.112 mm2 (or 12 %) difference in the cross section of fully hydrated oocytes just previous to ovulation. On the other hand there was no inverse relationship between OM oocyte size at spawning and batch fecundity. Ambient SST was not an important determinant of hydrated oocyte size since the same 12 % difference in oocyte size was estimated for the entire SST range of the study. We suggest that these stage-specific differences in the effect of maternal size on oocyte size are due to a functional relationship between the abdominal volume and ovarian size.

Saturday, June 27, 2015

Assessing species and stage specific effects of preservation on fish oocytes over different temporal scales

8:14 PM – by
Assessing species and stage specific effects of preservation on fish oocytes over different temporal scales

M. RAKKA, K. GANIAS

Abstract


This study assessed the effect of 10% neutral buffered formalin and of three ethanol solutions of different concentration on Mediterranean sardine and European anchovy oocytes over several temporal scales (days, weeks, months). The two species exhibit differences both in the elemental composition and the shape of their oocytes which further allowed an appraisal of oocyte shrinkage dynamics in relation to oocyte shape, developmental stage and composition. We showed that the effect of the preservative on oocyte size is stage specific while different preservation periods of ovarian material might lead to discrepancies among studies.

Keywords


sardine; anchovy; preservation protocols; spawning frequency; fecundity; reproductive biology

DOI: 10.12681/mms.1205

Sunday, March 8, 2015

Understanding the determinate–indeterminate fecundity dichotomy in fish populations using a temperature dependent oocyte growth model

2:10 PM – by
Understanding the determinate–indeterminate fecundity dichotomy in fish populations using a temperature dependent oocyte growth model

Understanding the determinate–indeterminate fecundity dichotomy in fish populations using a temperature dependent oocyte growth model

Highlights

•
We modeled the fecundity type in fishes based on the relationship between oocyte growth period and duration of spawning.
•
Simulations showed that stocks with OGP longer than the SP are predicted to exhibit determinate fecundity and vice versa.
•
Oocyte size frequencies and time trends in fecundity match descriptions for determinate and indeterminate spawners.

Abstract

The fecundity type (determinate vs. indeterminate) is still uncertain for many commercially important fish populations affecting accuracy in fecundity estimations and hindering the selection of appropriate egg production methods for stock assessment purposes. It is broadly considered that boreal fish populations living in colder habitats are determinate spawners whilst populations residing in warmer habitats tend to be indeterminate spawners. In the present study we modelled the determinate–indeterminate fecundity type in batch spawning fishes, i.e. fish that spawn several batches of eggs per spawning season, based on the relationship between oocyte growth period and the duration of the spawning period considering that both variables can be affected by water temperature and latitudinal distributions. Individual based models (IBMs) were developed to explore how the interaction of these variables can result in a series of patterns along the continuum from extreme determinacy, i.e. annual fecundity being recruited long before the onset of the spawning period, to indeterminacy. Model simulations showed that fish stocks with oocyte growth periods longer than the spawning period are predicted to exhibit determinate fecundity which provides a fair justification for why cold water species with slow oocyte growth and limited spawning periods are determinate spawners and vice versa.

Keywords

  • Fecundity type; 
  • Spawning season; 
  • Oocyte growth; 
  • Individual based models;
  • Determinate spawners; 
  • Indeterminate spawners

Application of GAMs and multinomial models to assess the spawning pattern of fishes with daily spawning synchronicity: A case study in the European anchovy (Engraulis encrasicolus) in the central Mediterranean Sea

2:09 PM – by

Monday, November 17, 2014

Friday, June 27, 2014

Evaluation of spawning frequency in a Mediterranean sardine population (Sardina pilchardus sardina)

1:46 AM – by

Ganias K., Somarakis S., Machias A., Theodorou A. (2003). Evaluation of spawning frequency in a Mediterranean sardine population (Sardina pilchardus sardina). Marine Biology, 142: 1169-1179
Abstract
The postovulatory follicle method was used to assess the frequency of spawning of sardine (Sardina pilchardus sardina) in the Central Aegean Sea (eastern Mediterranean) in November–December 1999 and 2000. A field-based aging key for postovulatory follicles (POFs) was developed, and preliminary evidence is presented of a temperature influence on the degeneration of POFs. Bias in the fraction of day-0 spawners (females that had, were, or would spawn the night of sampling) with respect to sampling time was identified and attributed to spawning behavior. An appraisal of consistency in spawners' fractions and sex ratio, based on four sets of sequential trawl hauls, showed a considerably high small-scale variability, which suggested that spawning schools are structures limited in space and/or ephemeral in time. Sampling gear, i.e. commercial purse seines and research pelagic trawls, did not differ significantly with respect to spawners' fractions. The fractions of day-1 and day-2 females were the same during both years, and their combination resulted in more precise, composite estimates of spawning frequency. In both years, the Mediterranean sardine spawned every 11–12 days. The incidence of spawning increased significantly with fish size. When compared to all estimates available for other sardine genera, species and subspecies, the spawning frequency of the Mediterranean sardine was lower; this was attributed to the synergetic effect of oligotrophy and smaller body sizes in the Mediterranean.


Ovarian atresia in the Mediterranean sardine, Sardina pilchardus sardina

1:46 AM – by

Ovarian atresia in the Mediterranean sardine, Sardina pilchardus sardina
K. Ganias,S. Somarakis,C. Koutsikopoulos,A. Machias and A. Theodorou (2003).
Journal of the Marine Biological Association of the UK, Volume 83, Issue06, December 2003 pp 1327-1332
http://journals.cambridge.org/action/displayAbstract?aid=191217
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