Browsing by Author "Ojeda, F. Patricio"

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    Description and discrimination of sagittae otoliths of two sympatric labrisomid blennies Auchenionchus crinitus and Auchenionchus microcirrhis using morphometric analyses
    (2021) Cerda, Jose Miguel; Palacios-Fuentes, Pamela; Diaz-Santana-Iturrios, Mariana; Ojeda, F. Patricio
    Auchenionchus crinitus and Auchenionchus microcirrhis share their distributional area along the Chilean coast. These labrisomid blennies are difficult to recognize based on the attributes described in taxonomic keys, which consist of overlapped or non-informative morphological and meristic characteristics of body parts. Sagittae otolith shape is useful for species determination; thus, the aim of our study was to evaluate the discriminant power of sagittae otoliths through analyses of shape indices and geometric morphometrics, and to describe the sagittae otolith shape of the two fish species. Four linear measurements (length, width, area and perimeter) of sagittae otoliths were considered to calculate the shape indices. Inter-specific differences were assessed by MannWhitney U tests for each index, and no significant differences between species were found (U = 181.5-256; p > 0.05). Based on these results, the shape indices evaluated here must not be employed for species of the genus Auchenionchus. A total of 72 landmarks contouring sagittae otoliths were considered for the geometric morphometric analysis, where the least-squares Procrustes method was followed to obtain a consensus coordinate matrix. The sagittae otolith was morphologically distinctive for each species, A. crinitus shows a wide and curved rostrum compared with A. microcirrhis, where this feature is more angled and elongated. Similarly, the posterior edge in the otolith of A. crinitus is wide in curvature, while this portion is angled in curvature in A. microcirrhis. The vertex between rostrum and anti-rostrum forms a cordiform shape in the sagittae otolith of both species, although in A. crinitus this characteristic is more prominent. A Principal Component Analysis and a Discriminant Function Analysis using the consensus coordinate matrix allowed us to confirm the differences between species according to sagittae otolith shape. Our study constitutes the first assessment of sagittae otolith shape via geometric morphometrics in the family Labrisomidae.
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    Feeding, and nutritional ecology of the edible sea urchin Loxechinus albus in the northern Chilean coast
    (2008) Gonzalez, Solange J.; Caceres, Cristian W.; Ojeda, F. Patricio
    The red sea urchin Loxechinus albus, in economically important species occurring along the Chilean littoral benthic systems, has been heavily exploited by artisanal fisheries in recent decades. However, basic knowledge of its trophic biology is still scarce. Studies of this kind are critical to the successful development of farming techniques as an alternative to the harvest of natural populations. The aims of this study were to quantify the composition of L. albus' natural diet, to determine the assimilation efficiency of the most important dietary components, and to experimentally examine the species' trophic selectivity. Adult and juvenile specimens were sampled in spring 1993 and summer, fall and winter 1994 from the shallow subtidal zone of Iquique, northern Chile. Neither juveniles nor adults showed significant seasonal differences in dietary composition. The main items in the diet were the green alga Ulva sp. for juveniles and the kelp Lessonia sp. for adults. In adults, assimilation efficiency (as percentage of the total organic matter ingested) was not significantly different among individuals that consumed Lessonia sp. (48.7%), U/va sp. (44.6%) and Macrocystis (38.1%), whereas in juveniles assimilation efficiency was significantly higher for individuals fed on the chlorophyte Ulva sp. (55.4%), followed by Lessonia sp. (35.0%) and Macrocystis (25.5%). These results suggest that L. albus undergoes an ontogenetic shift in the diet, consisting of a differential foraging strategy between juveniles and adults.
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    Inter-annual variability in somatic growth rates and mortality of coastal fishes off central Chile
    (2006) Hernandez-Miranda, Eduardo; Ojeda, F. Patricio
    The effects of El Nino (EN) and La Nina (LN) events upon marine organisms inhabiting the Eastern Pacific coast have been widely studied in recent years, concentrating primarily on changes in species composition and on population size. In this study, using somatic growth rates as metabolic response variables, we evaluated the mortality rates of coastal fishes inhabiting a central Chilean upwelling marine ecosystem in the South Pacific between 1990 and 2003. Four coastal fish species belonging to different trophic levels (one herbivore, one omnivore, and two carnivores) were analyzed. In all species, the estimated cohort somatic growth rates were low for those recruited during EN and high for those recruited during LN events. Annual cohort mortality rates were highest during EN events and lower during LN and transitional years. We propose that productivity (as a bottom-up driver) acts as a primary exogenous factor upon annual cohort mortality rates. We also propose that a plausible mechanism underlying this process is the negative effect the low somatic growth rates may have on fish ecological attributes such as their competitive abilities, condition factors, and predation risks, which ultimately may affect their fitness.
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    Ontogenetic pattern of resource use by the tiny hermit crab Pagurus villosus (PAGURIDAE) from the temperate Chilean coast
    (2007) Pardo, L. Miguel; Piraud, Fernanda; Mantelatto, Fernando L.; Ojeda, F. Patricio
    The biology of hermit crabs in the temperate zone is understudied in comparison with hermit crabs in the tropics and subtropics. Here we provide the first observations of population traits of the smallest South Pacific hermit crab, Pagurus villosus, using descriptive and experimental approaches. The principal emphasis is on ontogenetic and spatio-temporal variation in the breeding season, recruitment, sex ratio, microhabitat use, and shell occupancy pattern. We also experimentally evaluated colonization rates, in order to assess the pattern of habitat use. P. villosus showed continuous reproduction and recruitment, and an unbiased sex ratio. Algae turf was the microhabitat with highest record of individuals, regardless of their ontogenetic stage. Females were smaller and showed less movement activity on experimental trays than did males, for three microhabitat analyses. Early stages colonized higher proportions of artificial algae and shell hash (only juveniles). Diversity of gastropod shells used by hermit crabs (12 in total) decreased during development, but for all stages Tegula tridentata and Nassarius gayi were the most used. Females in different reproductive conditions (ovigerous and non-ovigerous) showed a shift of shell occupancy pattern likely related to the tradeoff between fitness and shape, weight, thickness and internal volume of shells. Population and life-history traits, i.e., continuous breeding and high resource use during all ontogenetic phases (microhabitats and shells), of P. villosus on the temperate Chilean coast seem more similar to pagurid species from low latitudes. These traits may reflect a tropical origin of this species and/or an adaptive strategy of these tiny crabs in a temperate region. (C) 2007 Elsevier B.V. All rights reserved.
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    Predator tactics and prey densities modulate the strength of trophic interactions in a temperate rocky reef
    (2021) Munoz-Cordovez, Rodrigo H.; Carrasco, Sergio A.; Ojeda, F. Patricio; Perez-Matus, Alejandro
    Evaluating the species-specific effects of multiple predators on shared prey helps to identify the mechanisms regulating predator impacts. Here, we investigate the trophic impact of two predators of the Chilean rocky subtidal, the fish Graus nigra [F] and the octopus Robsonella fontaniana [O] on their shared prey, the porcelain crab, Petrolisthes violaceus. Manipulative laboratory experiments were performed to evaluate mortality and behavior of porcelain crab in different treatments, including prey alone; prey with single predator ([O] or [F]); and prey with combined predators ([F + F], [O + O], and [O + F]). Different prey densities (N = 3, 9, and 12 individuals) were used to explore density-dependent predation mortality for single and combined predators using an orthogonal (crossed) design that allows to tease apart the effects of predator taxonomic identity from prey density. Behavioral responses of interacting species were registered every 4 h for 2 consecutive days, and were used to identify predator foraging strategies and prey refuge use. Mortality values (proportional prey mortality and predator per capita consumption) were compared among treatments. Results indicated differences in mortality among treatments. The cause of increase of prey proportional mortality was due to an increase in prey availability outside the refuge in fish treatments at high initial prey densities, while it was density independent in octopus' treatments. Changes in predator per capita consumption were registered depending on the predator combination and the initial prey density. These patterns may reflect contrasting predator foraging strategies and changes in refuge use by porcelain crabs, suggesting effects on prey mortality and predator impacts.
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    Recent diversification in an ancient lineage of Notothenioid fishes (Bovichtus: Notothenioidei)
    (2019) Near, Thomas J.; Ghezelayagh, Ava; Ojeda, F. Patricio; Dornburg, Alex
    Notothenioids are among the most intensively studied lineages of marine fishes. However, notothenioid research is predominately focused on the approximately 100 species of Antarctic cryonotothenioids. Far less attention is devoted to the non-Antarctic lineages Bovichtidae, Pseudaphritis urvillii, and Eleginops maclovinus, all of which originated prior to the diversification of cryonotothenioid species. Here we utilize DNA sequence data from mitochondrial and nuclear genes, as well as meristic trait morphology to investigate the evolutionary history of Bovichtidae. Bovichtus is the only polytypic lineage of early diverging non-Antarctic notothenioids providing a unique opportunity to contextualize the diversification dynamics of cryonotothenioids with their non-Antarctic relatives. We find strong evidence that species of Bovichtus represent a recent evolutionary radiation with divergence times similar to those estimated among the most closely related species of cryonotothenioids. The divergence in traditional meristic trait morphology among species of Bovichtus is consistent with their phylogenetic relationships. The phylogeny of Bovichtus implies the wide geographic distribution of species in the clade is likely the result of West Wind drift-driven dispersal. The phylogeny and divergence time estimates results reject a hypothesis that species persistence in Bovichtus reflects long periods of evolutionary stasis. Instead, we hypothesize that patterns of extinction and diversification in Bovichtus closely mirror those observed in their Antarctic relatives.
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    Temporal and spatial dissimilarities in an intertidal fish assemblage in the South Pacific Ocean: The role of the ENSO process and intrinsic habitat conditions in emerging patterns
    (2023) Espinoza, C. Valeria; Hernandez-Miranda, Eduardo; Gilabert, Horacio; Ojeda, F. Patricio
    An intertidal fish assemblage was studied in central Chile for 15 years in three localities: Isla Negra, El Tabo, and Las Cruces. Analyses of their multivariate dissimilarities were carried out considering temporal and spatial factors. Temporal factors included intra-annual and year-to-year variability. Spatial factors included locality, intertidal tidepool height, and each tidepool considered as a unique unit. Complementary to this, we tested the hypothesis that the El Nino Southern Oscillation (ENSO) would help explain year-to-year dissimilarities in the multivariate structure of this fish assemblage for the 15 years of data. To this end, the ENSO was regarded as a continuous inter-annual process as well as a set of discrete events. Additionally, dissimilarities in the temporal dynamics of the fish assemblage were evaluated considering each locality and tidepool unique units. Results indicated the following: (i) The most representative species for the whole area and period of the study were Scartichthys viridis (44 %), Helcogrammoides chilensis (17 %), Girella laevifrons (10 %), Graus nigra (7 %), Auchenionchus microcirrhis (5 %), and Helcogrammoides cunninghami (4 %); (ii) there is intra-annual (i.e., seasonality) and year-to-year multivariate variability in fish assemblage dissimilarities throughout the entire area of study, including all the tidepools and localities; (iii) when considering the spatial factor specifically, each tidepool unit, as well as their heights and localities, presented their own unique temporal yearto-year dynamics. The latter can be explained by the ENSO factor, also considering the intensity of the El Nino and La Nina events. In summary, the multivariate structure of the intertidal fish assemblage was statistically dissimilar when
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    Using expert knowledge to propose recreational marine reef-fish management measures in Chile
    (2024) Estevez, Rodrigo A.; Godoy, Natalio; Araya, Miguel; Azocar, Cristian; de la Barra, Christian; Bardi, Francisca; Fernandez-Urzua, Francisco; Garcia, Marcelo; Hiriart-Bertrand, Luciano; Lomonico, Serena; Medina, Marianela; Naretto, Javier; Ojeda, F. Patricio; Pequeno, German; Ponce, Francisco; Pulgar, Jose; Perez-Matus, Alejandro; Rivera, Javier; Smith, Andres; Toro Da Ponte, Jorge; Torres-Canete, Felipe; Vasquez, Julio A.; Gelcich, Stefan
    Marine recreational fisheries often lack necessary information to perform assessments and develop sustainable management strategies. In Chile, although reef-fish fisheries have been signaled as overexploited, there are still no commercial or recreational regulations regarding bans, catch limits, or size limits. We implemented an expert elicitation protocol to propose management measures to regulate recreational reef-fish harvests of 17 reef-fish species. Sixteen experts estimated minimum legal sizes, temporal closures, and maximum number of individuals harvested per person per trip (known as "bag limits"). Experts also prioritized management measures for each of 17 reef-fish species. Maximum number of individuals harvested per person per trip varied between 1 and 7. In addition, permanent bans were recommended for some species, such as acha (Medialuna ancietae), pejeperro (Semicossyphus darwini), and San Pedro (Oplegnathus insignis). We concluded that information gathered through expert elicitation can play a key role to inform data-poor recreational fishery management. Expert elicitation protocols that include iterative process, based on individual estimates and an open expert discussion phase, provide the necessary enabling environment to identify a variety of management measures. While future challenges include the development of mechanisms to promote acceptability and compliance for recreational fisheries management, the approach presented here is important to initiate much needed discussions.