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Efeitos ambientais nas condições de crescimento dos estados larvares de Sardina pilchardus na costa portuguesa e Golfo de Cádis
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Resumo(s)
Compreender a variabilidade de recrutamento de pequenos peixes pelágicos é essencial no estudo da
dinâmica das populações. O sucesso do recrutamento está intrinsecamente relacionado com as condições
ambientais, sendo a temperatura e a disponibilidade de alimento os fatores principais que se identificam
como influenciando a sobrevivência dos estágios iniciais de desenvolvimento. No presente estudo,
analisámos a condição nutricional e o crescimento de larvas da Sardina pilchardus ao largo da costa
portuguesa no início e no final da época de desova, em condições ambientais distintas. Determinou-se
para cada larvar o número de incrementos dos otólitos e a largura dos três últimos incrementos, bem
como o peso seco e o conteúdo em DNA das larvas. Modelos aditivos generalizados (GAM) foram
usados para examinar a influência de variáveis ambientais na distribuição das larvas e nas taxas de
crescimento individual. No início da época de desova (final do Outono) as larvas encontraram-se
principalmente junto da foz dos rios onde as massas de água são mais produtivas e mais frias. Na
primavera, quando as altas concentrações de clorofila-a se estendem para uma área mais ampla, os
estágios larvares da sardinha estavam distribuídos de uma forma mais homogénea em toda a área
rastreada. Durante o outono, o crescimento larval foi maior na costa oeste ibérica comparado com o
crescimento observado na primavera nas costas oeste e sul, o que provavelmente, está relacionado com
a temperatura mais elevada. O crescimento aumentou com o aumento de Chla e de temperatura. A
condição nutricional das larvas de sardinha foi maior durante a primavera na costa oeste comparada com
o outono. Larvas em maior condição nutricional ocorreram em áreas com menor temperatura e
salinidade. Este trabalho permitiu estender a nossa compreensão sobre os fatores ambientais que afetam
o crescimento e a sobrevivência das larvas da sardinha ao largo da costa continental portuguesa.
Understanding recruitment variability of small pelagic fish is essential in the study of dynamics of the populations. Main drivers of recruitment success are sought to be environmental conditions such as temperature and food availability influencing survival of the early life stages. In the present study, we analyse the nutritional condition and growth of the larvae of the European sardine, Sardina pilchardus, off the Portuguese coast at the beginning and in the end of the spawning season, when larvae experience distinct environmental conditions. The number of increments and the width of the last three increments were determined on the otoliths and the dry weight and DNA content were analysed for the same larvae. Generalized additive models (GAM) were used to examine the influence of environmental variables on larvae distribution and individual growth rates. At the beginning of the spawning season (late autumn) larvae were found mainly in the vicinity of river freshwater runoff, restricted to the more productive and colder water masses. During spring, when high chlorophyll-a concentrations extend to a wider area, sardine larval stages were more homogeneously distributed throughout the surveyed area. Larval growth was higher during the fall off the western Iberian coast when compared to the spring off the west and south coasts, which is probably related to the higher temperature. Growth increased with increasing Chla and higher temperature. Nutritional condition of sardine larvae was higher during spring in the west coast when compared to the fall. Larvae in higher nutritional condition occurred in areas with lower temperature and salinity. This work allowed to advance our understanding of the environmental factors impacting growth and survival of sardine larvae off the Portuguese continental coast.
Understanding recruitment variability of small pelagic fish is essential in the study of dynamics of the populations. Main drivers of recruitment success are sought to be environmental conditions such as temperature and food availability influencing survival of the early life stages. In the present study, we analyse the nutritional condition and growth of the larvae of the European sardine, Sardina pilchardus, off the Portuguese coast at the beginning and in the end of the spawning season, when larvae experience distinct environmental conditions. The number of increments and the width of the last three increments were determined on the otoliths and the dry weight and DNA content were analysed for the same larvae. Generalized additive models (GAM) were used to examine the influence of environmental variables on larvae distribution and individual growth rates. At the beginning of the spawning season (late autumn) larvae were found mainly in the vicinity of river freshwater runoff, restricted to the more productive and colder water masses. During spring, when high chlorophyll-a concentrations extend to a wider area, sardine larval stages were more homogeneously distributed throughout the surveyed area. Larval growth was higher during the fall off the western Iberian coast when compared to the spring off the west and south coasts, which is probably related to the higher temperature. Growth increased with increasing Chla and higher temperature. Nutritional condition of sardine larvae was higher during spring in the west coast when compared to the fall. Larvae in higher nutritional condition occurred in areas with lower temperature and salinity. This work allowed to advance our understanding of the environmental factors impacting growth and survival of sardine larvae off the Portuguese continental coast.
Descrição
Tese de Mestrado, Ecologia Marinha, 2023, Universidade de Lisboa, Faculdade de Ciências
Palavras-chave
Microestrutura dos otólitos Larvas de peixe DNA mg-1 Sardina plichardus Teses de mestrado - 2023