Bioenergetics of small pelagic fishes in upwelling systems: relationship between fish condition, coastal ecosystem dynamics and fisheries (original) (raw)
Related papers
Biochemical ecology of small pelagic fishes: the linkage between environment and fisheries
Marine Ecology Progress Series
Coastal upwelling ecosystems provide the bulk of the world's fishery yields, but the biochemical ecology of the species that make up these fisheries has, surprisingly, been ignored. Biochemical indicators can provide a mechanistic, ecosystem-based link between population and ecosystem dynamics. Here we investigated long-term, inter-annual changes in the proximate composition and energetic condition of European sardine Sardina pilchardus and its relationship with oceanographic conditions in the Western Iberian Upwelling Ecosystem. Energy density (ED) ranged between 4.0 and 14.2 kJ g-1 , and the seasonal cycle largely determined temporal variability, explaining > 80% of the observed variation. ED variations were also closely linked with water (total R 2 = 99.0% in whole body; total R 2 = 95.0% in muscle) and lipid dynamics (total R 2 = 99.6% in whole body; total R 2 = 92.5% in muscle). After adjusting for seasonality (rED) and restricting the temporal analysis to the end of the feeding period (August to October), spring/early-summer oceanographic conditions explained 67% of the late-summer energetic peak. Interestingly, the sardine rED peak in year (t) explained > 54.4% of the variation in the annual catches of year (t + 1), indicating that adult energetic condition during spawning is partially translated into the fishery through parental effects in recruitment strength. Our results support earlier findings indicating that sardine population dynamics seem to be controlled by bottom-up effects, but the linkages between population dynamics and patterns in environmental variability via physiological condition seem to have previously been overlooked. We also provide empirical evidence that biochemical assessments during critical periods of the life-cycle of fish are essential in understanding the population dynamics of coastal upwelling ecosystems and in developing a more solid basis for stock management and conservation.
Fishes
Information on the biological parameters of exploited fish stocks facilitates the objective assessment and management of these living resources. The sardine (Sardina pilchardus) is considered as overexploited in northwest Africa. It is a key species of the Canaries current large marine ecosystem (CCLME) of the Atlantic Ocean due to its socioeconomic importance, as well as being a key intermediary species in marine food web. A massive decline in caught fish for Senegal over half a century is also reported (61,648 t in 1994 to 7486 t in 2017). Here, we analyzed the age and growth parameters of sardines in the Exclusive Economic Zone of northern Senegal. Maximum body size was 31 cm total length (TL). A growth performance index (φ′) and a growth rate coefficient (K) of 2.65 and 0.85, respectively, were determined, with this being the first record for this country. Sardines had higher asymptotic length (L∞, 30.5 cm TL) and age (6 years) in northern Senegal compared with Morocco (Atlantic...
South African Journal of Marine Science, 2001
Time-series of condition factor (CF) and gonadosomatic index (GSI) were generated using general linear models (GLM) for sardine Sardinops sagax stocks in the northern and southern Benguela ecosystems over the period [1984][1985][1986][1987][1988][1989][1990][1991][1992][1993][1994][1995][1996][1997][1998][1999]. During this period the biomass of sardine in the northern Benguela remained at relatively low levels of < 500 000 tons, whereas that of southern Benguela sardine increased 40-fold to 1.3 million tons. The GLMs explained 27 and 45% of the observed variation in CF, and 32 and 28% of the observed variation in GSI, for sardine in the northern and southern Benguela subsystems respectively. Whereas the sardine CF in the northern Benguela remained stable over time, that for the southern Benguela stock declined steadily during the study period. Sardine CF showed a seasonal cycle in the southern but not in the northern Benguela. Time-series of GSI showed high interannual variability but no trends in either subsystem, and the seasonal pattern was similar for both stocks. The lack of coherence between the CF time-series for sardine in the two subsystems further suggests that sardine stocks in the northern and southern Benguela subsystems are independent.
Marine Ecology Progress Series
Since 2008, there has been a major decrease in the numbers of old and large sardines in the Gulf of Lions, which has had a major effect on regional fisheries. A bottom-up process involving a shift in diet towards smaller planktonic prey has been suggested as the main driver of this development. Yet, the reproductive capacities of the sardines have not changed, suggesting potential modifications in energy allocation trade-offs. Whether this could also affect maintenance, in particular at the end of the winter reproductive period, and explain the lower adult survival and the disappearance of older individuals remains unclear. We therefore experimentally investigated the consequences of seasonal food availability (summer vs. winter) on life-history traits and energy allocation trade-offs at the individual and population levels. Our results indicate that food resources during summer had a major effect on energy reserves and growth, limiting the maximum size and body condition reached at...
Scientia …, 2006
Late larval stages of sardine (16-23 mm) were sampled during the 2003 spawning season in their nursery grounds located off the Ebro river mouth, on the Catalan coast, and in two bays of the Alborán Sea coasts, the Bay of Almería and the Bay of Málaga. The daily growth analysis of each sampled population revealed faster growth in the Ebro sardine larvae than in both of the Alboran Sea larval populations. This fact is supported by their greater content with age of DNA, RNA and protein. However, the significantly higher carbohydrate content of the Bay of Almería sardine larvae and a higher Fulton's index, indicative of energy storage of individuals, in both of the sardine populations sampled in the Bays of Almería and Málaga show evident differences in the daily growth of the Alborán Sea larvae from those originating in the Ebro region. Late larval growth in the Alborán Sea sardine tends to favour an increase in body mass rather than in body length. This study hypothesises that the productivity pulses off the Alboran Sea coasts induced by the north and northwestern wind regimes may be responsible for the growth pulses observed in the otolith microstructure.
Marine Biology, 2008
Temporal variation in the fatty acid (FA) composition of stomach contents of Iberian sardines was compared to the relative contribution to dietary carbon made by diVerent prey types for Wsh from two areas oV Portugal. The eVect of the FA content of the diet on sardine muscle FA composition was also studied, aiming at (1) analysing if FA biomarkers can be used as a complementary technique for the study of sardine diet and (2) to relate spatial and temporal variations of prey FA content with sardine condition and reproduction. SigniWcant spatial diVerences in the FA composition of sardine diet occurred with concentrations of n-3 polyunsaturated FA, namely eicosapentaenoic acid [EPA, 20:5n-3] and linolenic acid 18:3n-3, being signiWcantly higher in the diet of sardines from the west coast, whilst the diet of sardines from the south coast was richer in monounsaturated fatty acids (MUFA), namely the carnivory biomarker oleic acid 18:1n-9. These results are in agreement with the higher contribution made by diatoms and dinoXagellates to the diet of sardines oV the west coast. Spatial variation in sardine dietary FA was also detected in their muscle composition, speciWcally for EPA, and the eicosapentaenoic/docosahexaenoic acid and (n-3)/ (n-6) ratios, which were higher in sardines from the west coast. No diVerence in FA composition was detected between sexes, and the seasonal variability in sardine total FA concentration was primarily related to the seasonality of spawning. Sardines accumulate high concentrations of FAs during the resting stage of reproduction when the feeding intensity is similar or lower to that observed during the spawning season. Additionally, sardines show a high selective retention of MUFA and polyunsaturated FA (PUFA) throughout the year except at the beginning of the spawning season, when these FAs are largely invested in the formation of the gonads. Therefore, temporal and regional diVerences of prey environments are strong enough to be reXected in Wsh body composition, namely on the accumulation of essential FAs, which can have a strong impact on reproduction success for this species.
Scientia Marina, 2006
Late larval stages of sardine (16-23 mm) were sampled during the 2003 spawning season in their nursery grounds located off the Ebro river mouth, on the Catalan coast, and in two bays of the Alborán Sea coasts, the Bay of Almería and the Bay of Málaga. The daily growth analysis of each sampled population revealed faster growth in the Ebro sardine larvae than in both of the Alboran Sea larval populations. This fact is supported by their greater content with age of DNA, RNA and protein. However, the significantly higher carbohydrate content of the Bay of Almería sardine larvae and a higher Fulton's index, indicative of energy storage of individuals, in both of the sardine populations sampled in the Bays of Almería and Málaga show evident differences in the daily growth of the Alborán Sea larvae from those originating in the Ebro region. Late larval growth in the Alborán Sea sardine tends to favour an increase in body mass rather than in body length. This study hypothesises that the productivity pulses off the Alboran Sea coasts induced by the north and northwestern wind regimes may be responsible for the growth pulses observed in the otolith microstructure.
Journal of Animal Ecology, 2014
1. Ecological systems are often characterized as stable entities. However, basal productivity in most ecosystems varies between seasons, particularly in subarctic and polar areas. How this variability affects higher trophic levels or entire food webs remains largely unknown, especially in these high-latitude regions. 2. We undertook a year-long study of benthic (macroinvertebrate) and pelagic (zooplankton) resource availability, along with short (day/days: stomach content)-, medium (month: liver d 13 C and d 15 N isotopes)-and long-term (season: muscle d 13 C and d 15 N isotopes) assessments of resource use by a generalist fish, the European whitefish, in a deep, oligotrophic, subarctic lake in northern Europe. Due to the long ice-covered winter period, we expected to find general benthic reliance throughout the year, but also a seasonal importance of zooplankton to the diet, somatic growth and gonadal development of whitefish. 3. Benthic and pelagic resource availability varied between seasons: peak littoral benthic macroinvertebrate density occurred in mid-winter, whereas maximum zooplankton density was observed in summer. Whitefish stomach content revealed a reliance on benthic prey items during winter and pelagic prey in summer. A seasonal shift from benthic to pelagic prey was evident in liver isotope ratios, but muscle isotope ratios indicated a year-round reliance on benthic macroinvertebrates. Whitefish activity levels as well as somatic and gonadal growth all peaked during the summer, coinciding with the zooplankton peak and the warmest water temperature. 4. Stable isotopes of muscle consistently depicted the most important resource, benthic macroinvertebrates, whereas short-term indicators, that is, diet and stable isotopes of liver, revealed the seasonal significance of pelagic zooplankton for somatic growth and gonad development. Seasonal variability in resource availability strongly influences consumer growth and reproduction and may also be important in other ecosystems facing pronounced annual weather fluctuations.
2020
We present main results of a systematic literature review and a temporal and spatialtemporal modelling exercise to investigate the main effects of environmental factors on anchovy and sardine biomass, abundance, occurrence and landings. During the systematic review, more than 1300 studies were evaluated and assessed to extract available information. Despite the numerous studies, only 40 studies provided quantitative information about relationships between anchovy and/or sardine and the environment. Available data was more abundant for anchovy than for sardine, and adults were more studied that eggs, larvae and juveniles (the least studied). Data was also heterogenically distributed in the Mediterranean Sea. [...]
Scientia Marina (Barcelona), 2003
In this study we present the longest time series available concerning various biological parameters of sardine in Greek waters. Biweekly samples were collected within a single day in clusters from random collections of the total landed catch derived from different vessels operating in the Northwest Aegean Sea, between July 1996 and June 2000. Total length (TL) was measured for 51.246 individuals. In addition, for a sub-sample of 50 individuals per sampling period, gross body weight and gonad weight were also measured to the nearest 0.1 and 0.01 g respectively. The analysis of the biweekly length-frequencies showed that the dominant length classes ranged between 130 and 160 mm TL. The mean biweekly TL decreased significantly (r=-0.525, P<0.05) with time during the study period. The same was also true for the maximum TL (r=-0.46, n=77, P<0.001). In contrast, the exponent b of the length-weight relationship increased significantly (r=0.358, P<0.05) with time. No relationship was found between the gonadosomatic index and b (r=-0.13, P>0.05). The parameters of the seasonalized von Bertalanffy growth equation and mortality and exploitation rates, based on monthly length-frequencies, were also estimated. The decline in the mean TL and the increase in the slope b of the length-weight relationship are discussed in relation to the recent increase in the effort expended on sardine populations and within the framework of density-dependent effects on growth.