An interference visual census technique applied to cryptobenthic fish assemblages

We compare the accuracy of an interference visual census technique (IVC), in which dismantling of the habitat is performed, to traditional underwater visual census (VC) and anaesthetic census. We compare the performance of these techniques applied to a temperate cryptobenthic fish assemblage using two strategies: sampling over the whole depth extent of the rocky bottom, and stratified sampling over the main microhabitats present at the study site. T h e number of species encountered was lower using the traditional VC. Fish density estimates were significantly higher using the interference technique compared to the traditional VC, in the transect strategy. These differences were larger for clingfishes and some gobies which occurred preferably under cobble and small rocks. No differences were found when comparing the IVC and anaesthetic census in the habitat strategy, for each microhabitat considered. We conclude that dismantling the habitat increases the performance of the visual census technique and is therefore a valuable approach when applied to temperate cryptobenthic fish assemblages

Patterns and processes of variation of a rocky bottom cryptobethic fish assemblage

Tese de dout., Ciências do Mar, Faculdade de Ciências do Mar e do Ambiente, Universidade do Algarve, 2006The population dynamics of criptobentic fishes in the Arrábida Marine Park was investigated. The fluctuations in composition and abundance, the duration of the pelagic phase and the choice of settlement habitats were assessed. A new non-destructive technique to count cryptobenthic fishes was tested. To study the larval phase we sampled the shallow rocky subtidal where we found mostly cryptobenthic species. Some of these species remain close to shore throughout the entire pelagic phase, e.g. Pomatoschistus pictus. The duration of the period spent in the plankton is variable within the cryptobenthic fishes but there are some, such as the Gobiesocidae, that spend very short periods as larvae. Lepadogaster lepadogaster settlers occur in higher abundances in high complexity habitats. An interference visual technique was described, tested and used to describe the composition of the cryptobenthic assemblage and assess its spatio-temporal variation. Several species use a restricted number of habitats (e.g. Gobius xanthocephalus and Tripterygion delaisi), whereas only one used all habitats available, Parablennius pilicornis. Moreover, the habitat utilization changed seasonally. Diversity and abundance of the cryptobenthic assemblage remained stable during two years and a consistent seasonal trend was observed. The peek in abundance coincided with the arrival of recruits, in the autumn, but there was a clear decrease in abundance in the subsequent seasons. The population dynamics of cryptobenthic fishes seems to be structured by post-settlement processes and can be understood by the particular ecological features displayed throughout their life-cycle.Esta tese analisa a dinâmica populacional dos peixes criptobênticos de substrato rochoso no Parque Marinho Luiz Saldanha. Foram estudadas as variações de composição e abundância durante a fase larvar e a fase juvenil/adulto, a duração da fase pelágica de algumas espécies criptobênticas, os habitats de assentamento e testou-se uma nova técnica de amostragem não destrutiva para peixes criptobênticos. No estudo da fase larvar foi amostrado o subtidal rochoso próximo da costa onde se capturam maioritariamente espécies criptobênticas a três profundidades distintas. As larvas mais desenvolvidas ocorreram em maior abundância a maior profundidade. Algumas destas espécies parecem permanecer junto à costa, por exemplo Pomatoschistus pictus, ao longo de toda a fase pelágica. A duração desta fase é variável mas há famílias como os Gobiesocidae que passam períodos curtos no plankton. Quando assentam alguns juvenis de Lepadogaster lepadogaster ocorrem em maiores abundâncias em habitats com elevada complexidade. A técnica de contagem visual com interferência demonstrou ser eficaz para contar peixes criptobentónicos e permitiu descrever a composição desta comunidade e analisar a sua variação espacio-temporal. Várias espécies usam um número restrito de habitats, (e.g. Gobius xanthocephalus e Tripterygion delaisi), e uma usa praticamente todos os habitats, Parablennius pilicornis. Adicionalmente, observou-se uma variação sazonal na utilização dos diferentes habitats. A diversidade e abundância dos peixes criptobênticos mantiveram-se estáveis ao longo de dois anos apresentando uma variação sazonal consistente. O pico de abundância coincidiu com a chegada de novos indivíduos no Outono mas subsequentemente registou-se um acentuado decréscimo. A dinâmica populacional dos peixes criptobênticos parece ser determinada por factores pós-assentamento e pode ser compreendida à luz das suas características ecológicas nas diferentes fases do seu ciclo de vida

Composition and temporal dynamics of a temperate rocky cryptobenthic fish assemblage

Temporal variation in a temperate cryptobenthic ¢sh assemblage at the Arra¤bida Marine Park (Portugal) was assessed by visual surveys during 2002 and 2003. A total of 9596 ¢sh from 11 families and 30 species was recorded. There were no changes in structure or density at the assemblage level between years, whereas diversity changed signi¢cantly due to a higher number of abundant species in the second year. A similar seasonal trend was found between years, with a signi¢cant overall density increase in autumn. This is partially explained by the arrival of new recruits of some of the most abundant species in the assemblage. Assemblage diversity and structure also changed across seasons. A group of species encompassing Gobius xanthocephalus,Tripterygion delaisi, Parablennius pilicornis, Gobius paganellus, Lepadogaster candollii and Lepadogaster spp. were analysed in detail. The temporal patterns of two of the most abundant species, G. xanthocephalus and T. delaisi, mimicked the overall temporal patterns of the assemblage.We suggest that the inter-annual stability in density of this subtidal ¢sh assemblage may be similar to what has been reported for the intertidal and that strong post-settlement processes are probably shaping this assemblage

Depth distribution of nearshore temperate fish larval assemblages near rocky substrates

In this study, we compare the composition, abundance and structure of a temperate fish larval assemblage at different depth intervals (0–4, 4–8 and 8–12 m) in the extreme nearshore environment. We used a plankton net attached to an underwater scooter to sample in close proximity to the rocky substrate (<50 cm). A total of 868 larvae from 27 taxa in 13 families were caught. The majority of larvae belonged to benthic reef-associated species (Blenniidae, Gobiidae, Gobiesocidae and Tripterygiidae), the four most abundant comprising 76% of the total larvae caught. A non-metric multidimensional scaling analysis (MDS) showed that there was a single multispecific larval patch near the substrate in the extreme nearshore up to 12 m depth. Nonetheless, distinct larval abundances were found in this relatively small depth range, with the majority of species being more abundant at the deepest interval, particularly Pomatoschistus pictus and Gobius xanthocephalus. Tripterygion delaisi was an exception being more abundant at the shallowest depth as young larvae. The density of pre-flexion larvae was not significantly different across depth intervals, but post-flexion larval density increased with depth. The full size range (from hatching to settlement) of P. pictus was present at the extreme nearshore. The innovative sampling technique used here revealed high densities of larvae close to the bottom, and depth was found to be an important factor influencing the distribution of several taxa and ontogenetic stages. The nearshore component of coastal fish larval assemblages near rocky substrates has been poorly studied, and our results suggest that the high densities of larvae found to aggregate in these environments must be taken into account when studying distribution and functional aspects of these assemblages

Vertical structure of very nearshore larval fish assemblages in a temperate rocky coast

Small-scale vertical patterns of larval distribution were studied at a very nearshore larval Wsh assemblage, during the spring–summer period of several years, at two depth strata (surface and bottom) using sub-surface and bottom trawls. A total of 4,589 larvae (2,016 from surface samples and 2,573 from bottom samples) belonging to 62 taxa included in 22 families were collected. Most larvae belonged to coastal species. Although inter-annual variations in larval density and diversity could be found, total larval abundance was always higher near the bottom whereas diversity was higher at the surface. A marked distinction between the structure of surface and bottom assemblages was found. Sixteen taxa explained 95% of the similarity among surface samples. Larvae which contributed most to this similarity included species like clupeiformes, sparids and serranids, and also blenniids, tripterygiids and some labrids. In the bottom samples, fewer species were present, with only six taxa, almost exclusively from species which lay demersal eggs, contributing to 95% of the similarity between samples. Larvae present at the surface were signiWcantly smaller than at the bottom. For some of the most abundant species found at the bottom, only small larvae occurred at the surface while the whole range of sizes was present at the bottom, indicating that larvae may be completing the entire pelagic phase near the adults’ habitat. These results indicate that larval retention near the reefs probably occurs for these species, although for others dispersal seems to be the prevailing mechanism

First record of Chromogobius britoi (Teleostei: Gobiidae) on the mainland European coast

Chromogobius britoi is a recently described and poorly studied goby currently known only from the Macaronesian islands of Madeira and the Canarian archipelago. This species was captured for the first time on the Atlantic mainland coast of Europe (at Arra´ bida Marine Park, Portugal). The habitat, depth preferences and morphological characters of the species are revised

Deep heat: a comparison of water temperature, anemone bleaching, anemonefish density and reproduction between shallow and mesophotic reefs

French Polynesia is experiencing increasing coral bleaching events in shallow waters triggered by thermal anomalies and marine heatwaves linked to climate change, a trend that is replicated worldwide. As sea surface thermal anomalies are assumed to lessen with depth, mesophotic deep reefs have been hypothesized to act as refuges from anthropogenic and natural disturbances, the ‘deep reef refugia hypothesis’ (DRRH). However, evidence supporting the DRRH is either inconclusive or conflicting. We address this by investigating four assumptions of the DRRH focusing on the symbiotic association between anemones and anemonefish. First, we compare long-term temperature conditions between shallow (8 m) and mesophotic sites (50 m) on the island of Moorea from 2011–2020. Second, we compare the densities of the orange-fin anemonefish, Amphiprion chrysopterus between shallow and mesophotic (down to 60 m) reefs across three archipelagos in French Polynesia. Finally, we compare the percentage of anemone bleaching, as well as anemonefish reproduction, between shallow and mesophotic reefs. We found that the water column was well mixed in the cooler austral winter months with only a 0.19 °C difference in temperature between depths, but in the warmer summer months mixing was reduced resulting in a 0.71–1.03 °C temperature difference. However, during thermal anomalies, despite a time lag in warm surface waters reaching mesophotic reefs, there was ultimately a 1.0 °C increase in water temperature at both 8 and 50 m, pushing temperatures over bleaching thresholds at both depths. As such, anemone bleaching was observed in mesophotic reefs during these thermal anomalies, but was buffered compared to the percentage of bleaching in shallower waters, which was nearly five times greater. Our large-scale sampling across French Polynesia found orange-fin anemonefish, A. chrysopterus, in mesophotic zones in two high islands and one atoll across two archipelagos, extending its bathymetric limit to 60 m; however, orange-fin anemonefish densities were either similar to, or 25–92 times lower than in shallower zones. Three spawning events were observed at 50 m, which occurred at a similar frequency to spawning on shallower reefs at the same date. Our findings of thermal anomalies and bleaching in mesophotic reefs, coupled with mainly lower densities of anemonefish in mesophotic populations, suggest that mesophotic reefs show only a limited ability to provide refugia from anthropogenic and natural disturbances

Adaptive effects of parental and developmental environments on offspring survival, growth and phenotype

1. Phenotypic adjustments to environmental variation are particularly relevant to cope with putative environmental mismatches often imposed by natal dispersal. 2. We used an intergenerational cross-transplant field-based experiment to evaluate the morphological and physiological effects of parental and postsettlement water flow environments on the orange-fin anemonefish Amphiprion chrysopterus through ontogeny (at pre- and postsettlement stages). 3. Offspring born from parents under high water flow had an 18% higher caudal fin aspect ratio (a compound measure of shape) at the presettlement stage, 10% slower growth after settlement, and 55% lower survival after settlement compared to offspring from low water flow parents. At the presettlement stage, caudal fin length was determined by parental caudal fin length. At the postsettlement stage, fish survived equally well with similar phenotypes in both high and low developmental flow environments. However, results suggest potential developmental phenotypic plasticity in caudal fin length, which increases more under low water flow during development. After settlement, growth was the only morphological or physiological trait that was associated with parental water flow, which was lower from parents under high flow, as was survival. 4. These results give important insights into the parental contribution, both genetic and nongenetic, in determining early offspring phenotype and subsequent growth and survival. Our results also suggest that offspring may possess flexibility to cope with a wide range of local environments including those different from their parents. Overall, the findings of this study show the fitness consequences of living in different environments and the likely trade-offs between parental and offspring fitness in a wild population

Physiological and behavioural effects of anemone bleaching on symbiont anemonefish in the wild

1. Climate change causes extreme heat waves that have induced worldwide mass coral bleaching. The impacts of temperature‐induced bleaching events on the loss of algal endosymbionts in both corals and anemones are well documented. However, the cascading impacts of bleaching on animals that live in association with corals and anemones are understudied. 2. We performed a field‐based experiment to investigate how host anemone bleaching affected the metabolic rate, growth, behaviour and survival of wild juvenile orange‐fin anemonefish Amphiprion chrysopterus over 1, 2 and (for survival) 9 months. 3. We found that the standard metabolic rate of anemonefish residing in bleached anemones decreased over time but was unaffected in fish from healthy anemones. Despite the reduced metabolic cost, the growth rate of fish from bleached anemones was significantly lower compared to fish from healthy anemones, suggesting that animals residing in bleached hosts are at an energetic disadvantage. This was corroborated by our finding that fish from bleached anemones spent more time out of their anemones, suggestive of a greater need to forage in the water column. However, fish from bleached anemones were overall less active and used less space around the anemone, resulting in a negative correlation between space use and survival after 4 weeks. 4. Our results provide insight into the physiological and behavioural effects of host bleaching on juvenile fish in the wild, and highlight how relatively short‐term thermal anomalies can have long‐lasting impacts beyond the bleached anemones or corals themselves