Reproductive biology of round sardinella (Sardinella aurita) in north-eastern Mediterranean (original) (raw)
Reproductive biology of round sardinella (Sardinella aurita) in the north-eastern Mediterranean
Scientia Marina
The reproductive biology of round sardinella, Sardinella aurita Valenciennes, 1847, was studied for die first time in the north-eastern Mediterranean Sea. Round sardinella has gained much attention lately because of its biomass increase, which might be the result of climatic changes occurring across the Mediterranean Sea. Monthly samples were collected on board commercial purse-seiners for two complete year cycles (September 2000 to August 2002). Round sardinella is a gonochoristic fish. The overall female to male ratio was not statistically different (P=0.34) from unity, although it varied monthly and with the length of the fish. The seasonal changes in the gonadosomatic index and the macroscopic characteristics of gonads showed that round sardinella in the northern Aegean spawns between May and July. Male round sardinella reach first sexual maturity at a smaller total length than females (155.0 and 168.3 mm respectively). Mean absolute fecundity (FA) increased exponentially with b...
2021
Understanding drivers of fish maturity is essential to predict the productivity, stability, and resiliency of exploited populations. Size at maturity for European sardine (Sardina pilchardus) in the Central Mediterranean Sea has never been published within rigorous peer review process. In the past, stock assessment working groups in the Mediterranean requested such information; however, the size at which 50% of the fish population reaches the sexual maturity (L50) often received weak estimates based on a single or few years of observation, which do not necessarily reflect the whole stock. To address this data gap for the Central Mediterranean Sea, the present research estimated size at maturity of European sardine in the Strait of Sicily. In the study period (2009–2017), sampled individuals exhibited significant differences in size range as well as in body condition and reproductive effort. Data also permitted a clear identification of the spawning season, starting in September–Octo...
Evaluation of spawning frequency in a Mediterranean sardine population (Sardina pilchardus sardina)
Marine Biology, 2003
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.
Fisheries Oceanography, 2006
Spawning habitats of two eastern Mediterranean sardine, Sardina pilchardus (Walbaum, 1792), stocks (coastal waters of central Aegean and Ionian Seas) are characterized from daily egg production method (DEPM) surveys conducted during the peak of the spawning period. The latter occurs earlier in the Aegean Sea (December) than in the less-productive Ionian Sea (February). Single-parameter quotient analysis showed that the preferred bottom depth for spawning was 40-90 m in both areas but sardine selected sites of increased zooplankton in the Aegean Sea during December and increased fluorescence in the Ionian Sea during February. Estimates of daily egg production (P) and spawning stock biomass (B) were about four times lower for the Ionian Sea (P ¼ 7.81 eggs m)2 , B ¼ 3652 tonnes) than the Aegean Sea (P ¼ 27.52 eggs m)2 , B ¼ 16 174 tonnes). We suggest that zooplankton biomass might not be sufficient to support sardine reproduction in the highly oligotrophic Ionian Sea where the very small sardine stock may rely on the late-winter phytoplankton bloom. Actively selecting sites with increased zooplankton or phytoplankton and feeding plasticity (the well-known switching from selective particle feeding to non-selective filter feeding in sardines) are interpreted as adaptations to grow and reproduce optimally at varying prey conditions. Despite differences in temperature and productivity regimes, reproductive performance of sardine in the Ionian Sea was very similar to that in the Aegean Sea during the peak of the spawning period. In comparing adult parameters from DEPM applications to Sardina and Sardinops stocks around the world, a highly significant linear relation emerged between mean batch fecundity (F) and mean weight of mature female (W, g) (F ¼ 0.364W, r 2 ¼ 0.98). The latter implies that, during the peak of the spawning period, mean relative batch fecundity (eggs g)1) of sardine is fairly constant in contrasting ecosystems around the world.
2021
Otoliths reading and length frequency distribution were used for age determination and growth estimation of Sardinella aurita (round sardinella) stock of Southern Atlantic coast of Morocco. Both otoliths' method for age determination and Bhattacharya’s method for length frequency analysis showed five age groups. The growth performance index revealed that there is significant accordance among method of length frequency distribution and otoliths reading for stock assessment studies of Sardinella aurita stock in the south of Morocco. The microscopic observation of female gonads using histology method was investigated for the first time in our study area and confirms the presence of five principal stages of ovary of sardinella aurita: immature, maturing virgin and recovering spent, mature (or pre-spawning phase), spawning, post-spawning or spent. In addition, our results of the fecundity showed that the mean relative fecundity obtained is estimated at 193 ± 98 oocytes/g which is low...
2017
e present study investigates aspects of the biology of round sardinella, Sardinella aurita (Valenciennes, ) collected from Dora and Tripoli (Lebanon) between September and September . A total of specimens were collected from catches of purse seines and gillnets. Data on fish total length (LT), total weight (WT), sex and maturity were obtained. e length–weight relationships showed positive allometry. An overall sex ratio was calculated to be F/M=.. e L were estimated to be . ± . cm and . ± . cm for males and females, respectively.
Parental effects in the European sardine Sardina pilchardus
Marine Ecology Progress Series, 2004
Positive parental effects, defined as the strategies displayed by sardine Sardina pilchardus adults to increase the survival of eggs and larvae, were studied off the coast of the Iberian Peninsula (Spain) by monthly sampling of eggs and larvae in Ría de Vigo, over a period of 4 yr. Two different parental strategies were observed over the spawning period: temporal variations in spawning intensity, and variation of egg quality. Sardine spawn outside the upwelling season, to avoid offshore transport of eggs and larvae to where food is less abundant. There is a negative correlation between the duration of embryonic development and egg organic content. Sardine employ a parental strategy that adapts the biochemical composition of eggs to the evolution of the temperature in the area during the spawning season. Eggs of higher organic content are produced in the coldest months, thereby compensating for the delay in embryonic development time due to low temperatures. This also has the effect of enhancing larval survival.
Journal of Fish Biology, 2019
We examined growth rates and reproductive characteristics of Sardinella aurita off Senegal and other coastal areas over a 20 year period (1995-2014) to determine how they relate to variations in environmental characteristics of coastal waters. Based on fish length-frequency data and a coastal upwelling index, we found that S. aurita recruitment tends to occur during the periods of most intensive upwelling (March-April off Senegal). Peak reproduction corresponds to periods of low sea-surface temperature (in February or March). The sex ratio was remarkably consistent during the 30 year study period and so was not affected by environmental changes. We hypothesise that S. aurita takes advantage of the higher zooplankton productivity that occurs in coastal waters when upwelling brings nutrient-rich water to the surface (i.e., it increases its growth rate and accumulates energy reserves for spawning). Growth performance appears to be strongly dependent on environmental conditions. The timing of spawning seems to occur when food (zooplankton) is most available for supplying the energy requirements needed by adults for spawning and early development of larvae. Environmental changes seem to have a significant effect on S. aurita growth and reproduction, which endorses their high phenotypic plasticity.
Reproduction of Mediterranean fishes
Fish and more: 3rd Mini FishBase Symposium. University Studio Press, Thessaloniki, 2005
The reproductive strategies of fishes have long been a central issue in fisheries biology, ecology, and management (eg, Beverton 1963, 1992; Balon 1975; Froese & Binohlan 2000, 2003; Froese & Pauly 2000). An exploited fish population reacts to increasing fishing effort, ie, as mortality increases, compensatory mechanisms take place, eg, in growth and recruitment such as changes in fecundity and survival as well as in size and age of first maturity (Ricker 1975;