Reproductive biology of round sardinella (Sardinella aurita) in north-eastern Mediterranean (original) (raw)
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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.
Study of reproduction of sardine , Sardina pilchardus in the North of Atlantic Moroccan area
2016
This work aims to analyze some aspects of biology of Sardina pilchardus sampled during a period between November 2014 and October 2015 in Casablanca area. The study of reproduction showed that the sex ratio is in favor of females. The females are dominant in all class sizes. The sardines sampled during the period of study present different stage of sexual maturity. This implies that there is a difference in the maturation period and emission of gametes between individuals of the population. We also noted a difference in the percentage of maturation with the seasons. The monthly evolution of the gonad index (RGS) aims to determine spawning periods for a full annual cycle. Sardine reproduces throughout the year and with a major peak in winter. The condition coefficient k evolves in the same way for both sexes. The sizes at first sexual maturity (L50) are 19.8 cm and 17.6 cm for males and females respectively.
Aacl Bioflux, 2015
The round sardinella, Sardinella aurita (Valenciennes, 1847), was sampled from ship research Al Amir Mouley Abdellah in the period between June and July 2015 (southern Atlantic sea, Morocco) in the area between Cape Boujdor and Cape Blanc. The present study is about reproduction, age and growth of the round sardinella. The sex ratio varies with length. Females are more numerous than males especially for the high size (>34.5). The estimated lengths of fish of which 50% were mature, were 25.54 and 23.73 cm for males and females respectively. Growth parameters estimated, using direct method of Von Bertalanffy, gave asymptotic length, L∞, 33.72 and 33.66 cm and curvature parameter, K, of 0.83 and 0.97 per year for females and males respectively. The comparison of growth parameters for round sardinella, from Mediterranean and Atlantic waters, indicated different growth patterns between the two areas. We determined that the growth of S. Aurita is fast, reaching the size of 19 cm in the...
Population Ecology, 2007
The decision of how to allocate surplus energy to reproduction and growth can have important effects on fish population dynamics as well as on other life history traits. The natural examples on the interrelationship between maternal growth and number of offspring produced in fishes are scarce. We tested the hypothesis that these traits are competing for resources by estimating maternal previous growth decisions, using back-calculation, and present reproduction, expressed as absolute fecundity, of female round sardinella (Sardinella aurita) in the northeastern Mediterranean Sea. Despite the overall increasing trend of fecundity with age, individual fecundity was negatively related to individual specific growth rate between the most recent annulus formation and spawning within ages. A decreasing trend between previous growth rate and present fecundity emerged, showing that round sardinella allocate increasingly less energy to growth with age and more into reproduction and that the previous growth decisions determine present fecundity.
The European sardine Sardina pilchardus (Walbaum, 1792) was sampled monthly (October 2000-September 2002, onboard the purse-seine fleet, at its main fishing ground (northern Aegean Sea) of the eastern Mediterranean Sea. Sardine's total length ranged from 9.1 to 17.3 cm. Ageing analysis showed that the lifespan of sardine in the area may reach 5 years. The two growth estimation equations were applied to the same dataset and produced slightly different growth parameter values (von Bertalanffy: L ∞ = 17.21 cm, Κ = 0.53 y -1 , t 0 = -1.28 y for females and L ∞ = 16.59 cm, Κ = 0.65 y -1 , t 0 = -1.22 y for males; Gompertz: L ∞ = 17.14 cm, Κ = 0.61 y -1 , t 0 = -0.86 y for females and L ∞ = 16.51 cm, Κ = 0.71 y -1 , t 0 = -0.78 y for males). Overall sex ratio was skewed towards females (F:M = 1.43, χ 2 = 150.9, P < 0.001) and differed among months and size classes. The different growth patterns are explained by natural mortality that was higher for males (1.4 y -1 ) than for females (1.2 y -1 ). Although size at maturity was lower for males (11.37 cm) than for females (11.65 cm), the L M /L ∞ ratio was similar (0.69 for males and 0.68 for females). Sardine's spawning in the northern Aegean occurs between October and March-April but the exact onset and duration of spawning may differ inter-annually as a result of environmental factors.