MATRIX: Understanding temperate reef fish connectivity

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Early life history of larvae and early juvenile Atlantic horse mackerel Trachurus trachurus off the Portuguese west coast

Publication . Van Beveren, Elisabeth; Klein, Maria; Serrão, Ester; Gonçalves, Emanuel J.; Borges, R.

Early life history traits (ELHTs) are key to understand recruitment patterns in marine animals. However, for reef fishes, studies on ELHTs are mainly focused on tropical systems and little is known for temperate reefs. In this study we used SMURFs (Standard Monitoring Units for the Recruitment of Reef Fishes) to collect fish in a temperate rocky reef system (Arrabida Marine Park, Portugal) on a weekly basis for three months during the recruitment period. Six sub-surface SMURFs sampled 2490 Atlantic horse mackerel (Trachurus trachurus) postlarvae and juveniles. Sagittal and lapilli otoliths were extracted from a subsample of 296 fish and ELHTs, such as size and age at settlement, growth rate and age at first secondary growth formation were examined. Additionally, we tested three growth curves and selected the best suited to back-calculate the hatching pattern based on the lengths of all sampled fish. Standard length ranged from 6.13 mm to 48.56 mm and subsampled fish were aged between 19 days to 44 days. Age and size at settlement were estimated between 19 days and 36 days for individuals of 6.13 mm and 24.95 mm, respectively. Otolith shape changed clearly with increasing age and, on average, secondary growth started to form on day 33 (+/-3 days). Age/length relationship was well described by a Gompertz growth model which was used to back-calculate hatching dates. Four distinct hatching cohorts were identified with fish of the earliest cohort showing a faster body and otolith growth. This study indicates that the nearshore environment might have an important role in the early growth, development and hence recruitment of Atlantic horse mackerel. Information on the early life history of Atlantic horse mackerel is key to understand recruitment processes for this economically and biologically important species. (C) 2016 Elsevier B.V. All rights reserved.

2016-07Journal article

Restricted

High interannual variability in connectivity and genetic pool of a temperate clingfish matches oceanographic transport predictions

Publication . Klein, Maria; Teixeira, Sara; Assis, J.; Serrão, Ester; Gonçalves, Emanuel J.; Borges, R.

Adults of most marine benthic and demersal fish are site-attached, with the dispersal of their larval stages ensuring connectivity among populations. In this study we aimed to infer spatial and temporal variation in population connectivity and dispersal of a marine fish species, using genetic tools and comparing these with oceanographic transport. We focused on an intertidal rocky reef fish species, the shore clingfish Lepadogaster lepadogaster, along the southwest Iberian Peninsula, in 2011 and 2012. We predicted high levels of self-recruitment and distinct populations, due to short pelagic larval duration and because all its developmental stages have previously been found near adult habitats. Genetic analyses based on microsatellites countered our prediction and a biophysical dispersal model showed that oceanographic transport was a good explanation for the patterns observed. Adult sub-populations separated by up to 300 km of coastline displayed no genetic differentiation, revealing a single connected population with larvae potentially dispersing long distances over hundreds of km. Despite this, parentage analysis performed on recruits from one focal site within the Marine Park of Arrabida (Portugal), revealed self-recruitment levels of 2.5% and 7.7% in 2011 and 2012, respectively, suggesting that both long-and short-distance dispersal play an important role in the replenishment of these populations. Population differentiation and patterns of dispersal, which were highly variable between years, could be linked to the variability inherent in local oceanographic processes. Overall, our measures of connectivity based on genetic and oceanographic data highlight the relevance of long-distance dispersal in determining the degree of connectivity, even in species with short pelagic larval durations.

2016-12Journal article

Open Access

Recruitment patterns and processes of coastal fish species in a temperate rocky reef

Publication . Klein, Maria; Borges, Rita Alexandra Duarte; Gonçalves, Emanuel; Caselle, Jennifer

Recruitment of marine fish is composed of several steps, e.g. larval dispersal, metamorphosis to the juvenile stage, settlement and post-settlement. Each step is influenced by biotic and abiotic mechanisms, leading to a large variability of recruitment in space and time. Recruitment is a highly complex ecological process that has an essential impact on the demography, dynamics, persistence and overall genetic structure of a population and on the connectivity among populations. Regarding demersal and benthic fish species the dispersal of eggs and larvae describes the main form of gene flow among populations and facilitates connectivity among populations. Our level of knowledge on patterns of recruitment, dispersal and connectivity of fish differs between tropical and temperate marine systems, especially regarding the nearshore system. Most recruitment studies from temperate areas have analysed pelagic species and demersal species of sandy bottoms that are of commercial interest. While studies on recruitment patterns of fish inhabiting reef systems have been conducted mostly in tropical systems, in temperate areas such studies, in particular with a fine time scale are less common. One reason might be that traditional sampling methods (e.g. underwater visual census) are difficult to operate in the temperate nearshore due to harsher sea conditions (strong wind, waves, and currents and low visibility). Furthermore, several previous studies have highlighted the lack of knowledge on larval dispersal and population connectivity for temperate demersal fish. Therefore, the objectives of this thesis were i) to study temporal and spatial patterns of recruitment of rocky reef associated and coastal fish species at a nearshore rocky reef; ii) to analyse the influence of environmental processes on temperate fish recruitment at a small within season and a larger inter-annual scale; iii) to describe early life history traits that can be relevant to recruitment and iv) to estimate larval dispersal and population connectivity of an intertidal rocky reef fish species along the south west Iberian Peninsula. In this thesis, the main study area was the Arrábida Marina Park at the dynamic west coast of Portugal which is part of the Iberian Peninsula Upwelling System. Here, the recruitment of a temperate nearshore fish assemblage was studied at various spatial and temporal scales by sampling fish with standardized collectors filled with artificial substrate. This included the analysis of recruitment patterns in relation with oceanographic processes through generalized additive modelling and multivariate analysis and the study of early life history traits (ELHT). Moreover, population connectivity and larval dispersal of a common intertidal reef fish were investigated through an interdisciplinary approach combining indirect and direct genetic tools with bio-physical modelling. Standardized recruitment collectors filled with plastic substrate and installed in the water column (SMURFs), performed better than other types investigated, mainly due to easier handling and replicability. This collector type was then used throughout the thesis and for the first time this type of recruit collector, registered as well the recruitment of a pelagic fish species, Trachurus trachurus. This was the most abundant species, followed by the benthopelagic Serranus hepatus and various other cryptobenthic and benthopelagic species. At a temporal scale, recruitment varied highly between weeks within the summer recruitment season and between three consecutive years of monitoring. Temporal variation of recruitment was found at a species level, but also on the structure of the recruitment assemblage and on the composition of biogeographic species groups. More temperate fish were collected in 2012 than in 2011 and 2013. On the other hand more warm-temperate fish were found in 2013. Within the study area, the recruitment pattern was highly patchy at a fine spatial scale (~20 m) but less different at a larger scale (1-10 km). Recruitment patterns were related with environmental conditions. The inter-annual variation of the structure of the recruitment assemblage was related to the environmental variables up-welling, SST and surface current. But, the interaction between abiotic factors and recruitment differed among species. Highest abundance of T. trachurus recruits was registered in 2011 and in this year recruitment peaks of T. trachurus occurred around the new moon phase. Additionally, recruitment was negatively correlated with upwelling. Four hatching cohorts were estimated through backcalculation of the hatching date and individuals from these cohorts differed regarding ELHTS. For example, the first cohort had a faster early fish growth. The larval dispersal and population connectivity study of this thesis indicated highly connected populations and potentially long-distance larval dispersal of the common rocky intertidal fish, Lepadogaster lepadogaster, despite its short pelagic larval duration. Still, the dispersal model revealed higher probabilities for larval retention and exponentially declining probabilities of dispersal with distance and the parentage analysis resulted in self-recruitment and short larval dispersal. These results indicate that both local recruitment and long-distance dispersal can play an important role in the replenishment of a population. Moreover, the population differentiation and patterns of larval dispersal of L. lepadogaster were highly variable between years and this could be explained by inter-annual variation in current patterns. In summary, in this thesis settlement (reef fish), nearshore recruitment (T. trachurus) and larval dispersal (L. lepadogaster), which can contribute to the overall patterns of recruitment of fish populations, exhibited clear temporal patterns. Furthermore, various interactions of these processes with abiotic factors were found, which highlight the important role of oceanographic processes in mediating patterns of recruitment and larval dispersal. Results are discussed in relation to variation of the adult’s reef fish assemblage of the Arrábida Marine Park and why the gained understanding is important for fishery and conservation management. Since knowledge on coastal fish recruitment, population connectivity and larval dispersal is available mostly for tropical coral reef systems, findings of this thesis can help to broaden our understanding of patterns and processes in temperate reef systems. Overall, this thesis demonstrates that a multidisciplinary study approach, combining ecology, oceanography and genetics, is necessary to improve our understanding of the highly complex, interactive process of recruitment.

2016-07-14Doctoral thesis

Open Access

Larval development and allometric growth of the black-faced blenny Tripterygion delaisi

Publication . Solomon, F. N.; Rodrigues, D.; Gonçalves, E. J.; Serrão, E. A.; Borges, R.

Larval development and allometric growth patterns of the black-faced blenny Tripterygion delaisi are described from a larval series (body length, L-B = 3.30-12.10 mm) caught by light traps at the Arrabida Marine Park, Portugal. Larvae of T. delaisi possess distinctive morphometric and meristic characteristics which can be used to identify this species from related taxa. Pigmentation is sparse but characteristic, consisting of pigmented eyes, gas bladder pigmentation in the dorsal region, anal pigmentation and a row of regularly spaced postanal ventral melanophores. This pattern is present from as early as the yolk-sac stage and persists throughout all stages with just the addition of head and caudal pigmentation during the flexion and postflexion stages, respectively. The majority of fin development (with the exception of the caudal fin), occurs in the later stages of development. Myomere counts range between 37 and 45 for all stages. Growth is allometric during larval development. When inflexion points of growth were detected, growth was found to be biphasic with the inflexion points occurring within a very narrow range of L-B (8.70-8.90 mm) close to the mean +/- S.D. (9.44 +/- 1.48 mm LB) of postflexion larvae. Considering allometric growth patterns and ontogenetic descriptions together, the first developmental phase includes the preflexion and flexion stage larvae, while the second phase characterises the postflexion larvae prior to the transition from larvae to juvenile. (C) 2017 The Fisheries Society of the British Isles

2017-06Journal article

Open Access