Papers by Adrián Madirolas
Fisheries Oceanography, Jun 1, 2001
The relative abundance of adult Argentine anchovies (Engraulis anchoita) and the thermal structur... more The relative abundance of adult Argentine anchovies (Engraulis anchoita) and the thermal structure of the sea between 41° and 45°30′S during four research surveys were compared. Acoustic data were collected while making parallel transects along which CTD (conductivity, temperature, depth) stations were regularly distributed. Anchovy abundance was related to both the sea surface temperature and the stratification of the water column, as classified according to the φ parameter of stability (Simpson, 1981). Regarding the whole water column, the sea temperatures where adult anchovies were recorded ranged from 8.5 to 16.5°C, but anchovy echo traces from waters above 14°C were obtained mainly at night. The sea surface temperature bounds for anchovy distribution were 11 and 17°C, with a preferential range between 12.5 and 16°C, but no absolute value of sea surface temperature was found to be most favourable for the species. The highest fish abundances were related to sharp thermal gradients, either horizontally recorded in frontal zones (≈ 0.02°C or more per km) or vertically associated to the occurrence of a thermocline (stability > 10 J m–3). Sea fronts seemed to be the axes for the distribution of anchovy shoals, and the annual changes in the positions of the fronts seemed to be followed by analogous changes in the locations of the main anchovy concentrations. Within thermally stratified areas and during the daytime, anchovies apparently preferred the thermocline layer or the layer immediately above that, although a few fish shoals were located below the thermocline.
Mackerel (Scomber japonicus) and the environmental conditions in the Buenos Aires shelf area of "... more Mackerel (Scomber japonicus) and the environmental conditions in the Buenos Aires shelf area of "El Rincón" (39°-40° 30' S). August 1996. In August 1996 acoustic methods were employed to estimate mackerel abundance in the Buenos Aires shelf area of "El Rincón" (4,287 mn 2), located between 39°-40° 30' S. Results showed a biomass estimate of 77,260 t. A SIMRAD EK-500 equipment operated with a 38 KHz split-beam transducer was used. Midwater fishing trawls were employed to identify echotraces and to collect mackerel samples. Trawls 4 and 5 were the most successful. Samples included only adult fish (310-470 mm Lt and ages ranging 2-11). Length and weight growth parameters and mortality rates were estimated. Analysis of the stomach contents revealed that mackerel was feeding exclusively on zooplankters over 2 mm length. The analysis of the characteristics (dimensions and density) of the mackerel shoals allowed to detect two areas of concentration above and below 40°S latitude. The northern area was characterized by relatively small schools of medium density similar to those of the Mar del Plata area. In the southern zone, large schools of high density that account for almost 92 % of the total biomass were found. Differences between both areas were also detected when plankton distribution was analysed. Higher abundances of the dinoflagellate Alexandrium tamarense corresponded to the southern area. On the contrary, higher zooplankton biomass was detected northerly of 40°S. From an oceanographic standpoint, the presence of mackerel was associated to relatively higher salinity values. As a result of the different data analysed it is suggested that, during this time of the year, the species shows a migratory pattern from the intermediate shelf to coastal areas.
Fisheries Research, May 1, 1995
This paper reports on the first pelagic survey on the southern Patagonian shelf. As a result of a... more This paper reports on the first pelagic survey on the southern Patagonian shelf. As a result of a joint Argentine-Russian cruise on board the R/V ‘Dmitry Stefanov’ carried out in the early autumn of 1992, a major nursery ground of Sprattus fuegensis was located in the coastal area off Santa Cruz and Tierra del Fuego.Forty-nine ichthyoplankton stations along 14 transects
Fisheries Research, Feb 1, 2011
The characterization of the acoustic recordings obtained by an echo sounder is the first step in ... more The characterization of the acoustic recordings obtained by an echo sounder is the first step in the process of identification and classification of marine organisms. This technique is essential for abundance estimation or for detailed ecological studies using acoustic methods. This paper presents echo recordings of Argentine short-fin squid (Illex argentinus) concentrations, collected during February in three pre-recruit bottom trawl assessment surveys (2006, 2007, and 2009) carried out by the INIDEP (National Institute for Fisheries Research and Development). The survey area was a region on the Patagonian Shelf (100-200 m depth) between 44 • S and 51 • S where pre recruits of I. argentinus South Patagonian Stock (16-29 cm ML) were feeding on dense aggregations of zooplankton. Advanced techniques were used for post-processing the acoustic data, including the generation of synthetic echograms and the use of recognition algorithms of geometric patterns. Data were collected at two ultrasonic frequencies: 38 and 120 kHz. Typically, squid pre-recruits aggregated in schools located on or near the bottom. Squid concentrations varied in size, shape, and volume backscattering coefficient (average S v). Squid schools echo traces usually overlapped with those of predators such as Argentine hake (Merluccius hubbsi) and prey such as amphipods (Themisto gaudichaudii). Results show how the frequency response of the sound scattering can help characterize the squid concentrations and differentiate them from the other main scatterers in the area. The average differential scattering of S v(120-38 kHz) was +5 dB for squid, while values of +18 dB and −1.6 dB corresponded to the amphipods and hake, respectively. Statistical analysis supported the validity of the differentiation method.
Journal of Sound and Vibration
A model for computing acoustic scattering by a swimbladdered fish with coupling to surrounding fi... more A model for computing acoustic scattering by a swimbladdered fish with coupling to surrounding fish tissue that is assumed to behave as a homogeneous fluid, is presented. Mathematically, this corresponds to considering the problem of two penetrable scatterers immersed in a homogeneous medium, one of which is wholly embedded in the other. The model is formulated in the frame of boundary integral equations whose solution is achieved using the Boundary Element Method (BEM) for a planar triangle mesh. The numerical implementation is verified against benchmark solutions reported in the literature. The model is then applied to a specimen of Merluccius hubbsi, whose morphometry was determined by CT scanning, for evaluating its forward and backscattering responses. From the acoustic scattering viewpoint, the swimbladder is considered as a gas-filled object while the flesh constituting the fish body acts like a weak scatterer. The numerical results suggest the swimbladder and the fish body responses, when fully coupled, can lead to substantial differences with respect to the simplified models normally in use in the area of aquatic ecosystem research.
Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 2016
ICES Journal of Marine Science, 2006
During December 1999, a transect 260 km long was carried out along the major axis of the Río de l... more During December 1999, a transect 260 km long was carried out along the major axis of the Río de la Plata estuary. Acoustic (120 kHz), oceanographic, and zooplankton sampling were performed to extract a continuous, quasi-synoptic acoustic view of the estuary's salt wedge. Three different zones were identified. The riverine and marine zones were characterized by vertically homogeneous water and low volume-backscattering strength (Sv). The mixohaline zone was characterized by a strong vertical salinity gradient and the highest Sv values. There were no relationships between the reflection value calculated from the salinity gradient and suspended matter (sediments) and measured Sv. The greatest abundance of acoustically detectable organisms was at the halocline depth, coincident with the echo recordings. The positions of the halocline and the two fronts were determined on the basis of aggregations of the different planktonic groups. The physical presence of the salt wedge, as shown b...
Revista de Investigación y Desarrollo …, 1996
... Engráulidos'. Palabras clave: Engraulis anchoita, evaluación acústica, estructura de pob... more ... Engráulidos'. Palabras clave: Engraulis anchoita, evaluación acústica, estructura de poblaciones, parámetros vitales. ... En dicho estrato tampoco se realizaron lances de pesca, y por lo tanto no fue considerado para la evaluación acústica. ...
Acta Acustica United With Acustica, Sep 15, 2015
The prolate spheroidal model is reexamined to simulate the backscattered target strength by afish... more The prolate spheroidal model is reexamined to simulate the backscattered target strength by afish through coherent treatment of the swimbladder (gas-filled spheroid)and fishbody (liquid-filled spheroid). The wavelength/fish size applicability range of the model is expanded via implementation of non-traditional algorithms to calculate the prolate spheroidal radial functions. Results demonstrate the relevance of including the fishbody backscatter contribution and the random nature of fishb ehavior to obtain good agreement between model predictions and measurements. The model wastested by comparison with direct measurements of acoustic backscattering target strength of caged fish(Percichthys trucha)using a38kHz split-beam echosounder.Reported values of measured maximum and averaged target strength (int he intensity domain)f rom gadoids (bladdered fish) and mackerel (bladderless fish) were also compared with model predictions. In all cases, agood agreement wasobtained when comparing simulated and measured results.
Scientia Marina, 1997
SUMMARY: Salt wedge is a quasi permanent feature at the Río de la Plata estuary, generating stron... more SUMMARY: Salt wedge is a quasi permanent feature at the Río de la Plata estuary, generating strong vertical density gradients. Zooplankton and ichthyoplankton organisms aggregated below the halocline were insonified utilizing a scientific echosounder ...
ICES Journal of Marine Science, 2003
During routine acoustic surveys for the assessment of fish abundance in the Argentine Sea, large-... more During routine acoustic surveys for the assessment of fish abundance in the Argentine Sea, large-scale, plankton-like scattering layers covering thousands of square nautical miles are commonly observed. Net sampling revealed that many of these scattering layers comprised gelatinous zooplankters aggregated in dense concentrations in the main. Even though echoes from gelatinous zooplankton are expected to be weak, because of the low reflectivity of their bodies, dense aggregations are capable of producing sound-scattering levels high enough to mask even the overlapping echoes from swimbladdered fish. The objective of this study is to relate the aggregations of four gelatinous species identified by means of nets to the presence of sound-scattering layers. Selected sections of echo recordings from aggregations of Lychnorhiza lucerna (Scyphozoa), Iasis zonaria (Salpidae), Mnemiopsis leidyi (Ctenophora), and Aequorea sp. (Hydrozoa) were obtained at 38 or 120 kHz, at different locations al...
Jellyfish Blooms: Ecological and Societal Importance, 2001
The gelatinous zooplankton, composed by members of different phyla (Cnidaria, Ctenophora, Tunicat... more The gelatinous zooplankton, composed by members of different phyla (Cnidaria, Ctenophora, Tunicata), are usually neglected in most studies about energy transfer in the marine trophic web, and often it is assumed that such soft-bodied fauna are trophic 'dead ends' in the food webs. In recent years, however, it has been shown that many fish species feed extensively on gelatinous zooplankton, while other species may feed on them occasionally when other food is scarce. We found that anchovies, Engraulis anchoita Hubbs & Marini, 1935, shoaled close to the Río de la Plata surface salinity front, where dense aggregations of the salp, Iasis zonaria (Pallas, 1774), were detected acoustically in May, 1994. Densities of non-gelatinous zooplankton were low at this interface, and anchovies fed on the salps. In this paper, we describe the environmental and biological conditions that led a normally planktivorous filter feeder E. anchoita to prey on gelatinous plankton.
Comunidades bentónicas en regiones de interés pesquero de la Argentina, 2017
Las pesquerías de arrastre de fondo pueden producir disturbios en las comunidades bentónicas y lo... more Las pesquerías de arrastre de fondo pueden producir disturbios en las comunidades bentónicas y los hábitats reduciendo la biomasa producción y biodiversidad, en este contexto, tanto los fondos duros o arrecifes naturales como artificiales juegan un importante rol como refugio, hábitats y aún sustrato para numerosos invertebrados y son además áreas menos propensas de sufrir disturbios por actividades de pesca comercial de arrastre. Razón por la cual algunos bancos sublitorales de la provincia de Buenos Aires han sido estudiados en distinta profundidad y procurando alcanzar distintos objetivos, buscando conocer las comunidades de aquellos fondos consolidados donde abundan peces de interés comercial, o comparando arrecifes naturales y artificiales a fin de conocer cuan miméticas son las comunidades desarrolladas en los pecios con respecto a los afloramientos rocosos, sean estos navíos sumergidos producto de hundimientos accidentales (naufragios) o programados para emplazar parques submarinos con fines recreativos (ej. buceo autónomo, pesca deportiva).Fil: Genzano, Gabriel Nestor. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; ArgentinaFil: Giberto, Diego Agustin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Subsede Instituto Nacional de Investigación y Desarrollo Pesquero; ArgentinaFil: Madirolas, Adrian Osvaldo. Instituto Nacional de Investigaciones y Desarrollo Pesquero; ArgentinaFil: Bremec, Claudia Silvia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentin
2017 IEEE/OES Acoustics in Underwater Geosciences Symposium (RIO Acoustics), 2017
In 2016 the Argentine Institute for Fisheries Research (INIDEP) initiated the building of a new F... more In 2016 the Argentine Institute for Fisheries Research (INIDEP) initiated the building of a new Fisheries and Oceanographic Research Vessel at the Armon shipyards, in Vigo, Spain. The new R/V, named Victor Angelescu after one of the pioneers in Fisheries science in Argentina, was designed and built to comply with stringent specifications. The R/V V. Angelescu will be a regional class ship with her 53 m length and 13 m width. The ship will have DP capabilities (class B) and will be driven by a tandem of two A/C motors of 1050 kW each. Power will come from an array of three diesel gen-sets generating 3120 kVA. The ship has to meet the ICES 209 guidelines for minimizing the radiation of noise into the sea. Hence, several aspects of the engineering obey to this goal, as the double resilient mountings of gen-sets and propulsion motors. The allocation of the numerous scientific instruments, including a full suite of acoustic systems and the necessary deck gear in a rather small sized pack...
2015 IEEE/OES Acoustics in Underwater Geosciences Symposium (RIO Acoustics), 2015
Hydroacoustic techniques are the most suitable means for the remote sensing of the aquatic enviro... more Hydroacoustic techniques are the most suitable means for the remote sensing of the aquatic environments. Passive acoustics is the action of receiving sounds originated by different sources in the surrounding medium. The sound waves produced by a source are captured by a hydrophone and can be used to identify its origin. When an array of hydrophones is used, the position of the sound source can also be determined. Many aquatic organisms are able to produce sound with different purposes. Crustacean species, such as crabs and lobsters, produce sounds by means of pincer movements and also due to friction between shells, enabling scientists to study their behavior by using acoustic receivers of the appropriate frequency bandwidth and receiving sensitivity. In this work we proposed the use of passive acoustics in order to study the performance of crab fishing gear. The determination of the time of entrance into the fishing pots and the period of their residence were of particular interest. In order to test this hypothesis, we registered sounds amplitudes from different fishing pots by means of low cost, homemade self-contained hydrophone recorders. We were able to register the exact time of cages settlement on the bottom and the moment when the first crab entered the pot. We recorded an increasing sound level due to the incremented number of captured organisms. These results will be useful to adjust current models used for crab abundance assessment and it is expected to achieve a greater accuracy.
2015 IEEE/OES Acoustics in Underwater Geosciences Symposium (RIO Acoustics), 2015
The distribution of fish in the water column, particularly of demersal species near the seabed, i... more The distribution of fish in the water column, particularly of demersal species near the seabed, is relevant to the detection and assessment of fish populations. Here, acoustic data recorded during six consecutive seasons on the Patagonian stock of argentine hake (Merluccius hubbsi) provided detailed information about the vertical distribution of the species along the acoustic track. It was determined that during the day, about 95% of individuals are located within the first ten meters above the bottom, and that almost half of them are concentrated in the first meter from it. An exponential function was found to represent this near-bottom distribution, with a marked positive gradient in the vicinity of the seabed. The height of the Acoustic Dead Zone (ADZ) was estimated and employed together with the true vertical distribution of fish to calculate correction factors for the nautical area scattering coefficient (NASC). Considering the closeness of fish to the bottom, a distribution variable is proposed, the demersality coefficient, which allows mapping the behavior of fish over the area of distribution, providing a tool for the analysis of distributional aspects of ecological importance.
Cuando se propaga sonido en un medio acuoso, este encuentra a su paso gran cantidad y variedad de... more Cuando se propaga sonido en un medio acuoso, este encuentra a su paso gran cantidad y variedad de inhomogeneidades correspondientes a discontinuidades en las propiedades fisicas del medio, tal como ocurre en el mar con las algas microscopicas fitoplanctonicas, zooplancton, particulas en suspension, cardumenes de peces,submarinos y gradientes termicos y salinos. Esas inhomogeneidades producen dispersion acustica debido a la interaccion entre la onda incidente y el medio dispersor. Este fenomeno depende de la frecuencia de la onda incidente, de las dimensiones y forma del dispersor y de sus propiedades fisicas y las del fluido en el que se transmiten las ondas. Las tecnicas actuales de medicion con fuentes ultrasonicas de banda angosta, como las utilizadas en las ecosondas modernas, habituales en pesquerias, se basan en el fenomeno de dispersion acustica para obtener informacion sobre las propiedades fisicas de los dispersores de volumen presentes en el oceano, lo que constituye una h...
2017 IEEE/OES Acoustics in Underwater Geosciences Symposium (RIO Acoustics), 2017
Fuegian sprat Sprattus fuegensis is the clupeiform fish distributed further south and the only sp... more Fuegian sprat Sprattus fuegensis is the clupeiform fish distributed further south and the only sprattus inhabiting South Western Atlantic Ocean (SWAO). The distribution area covers the sub-Antarctic waters of the SWAO, including the fuegian archipelago and the Beagle Channel. This species is the most abundant pelagic resource in the region and until today it is not exploited commercially. Many aspects of this ecosystem are still under-studied. The first scientific observations about the acoustics recordings of this species were documented by INIDEP (Instituto Nacional de Investigación y Desarrollo Pesquero) during 1995–1996. Since 2012, several seasonal acoustic studies were carried out at a more local scale, covering different zones of the Beagle channel by means small vessels operated by the Centro Austral de Investigaciones Científicas (CADIC-CONICET). During those cruises a SIMRAD ES-70 portable echosounder operating a Combi-D 38/200 kHz was used. Sprat aggregations were identif...
Review and summary of the acoustic assessments of Argentine anchovy (Engraulis anchoita) abundanc... more Review and summary of the acoustic assessments of Argentine anchovy (Engraulis anchoita) abundance performed between 1993-2008. The annual research planning of the Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP) includes at least two surveys to estimate the total biomass of Argentine anchovy Northern and Southern stocks. The assessment is performed using hydroacoustic techniques and the Daily Egg Production Method. In this paper the results of the acoustic estimates obtained during the 1993-2008 period are summarized. Besides, the studies performed to determine the characteristics of the species behavior such as vertical migrations or avoidance reactions to vessels that would produce uncertainty about estimates absolute value are discussed.
Engraulis anchoita is a physostomous fish with a dual chambered swim bladder (sb). In situ target... more Engraulis anchoita is a physostomous fish with a dual chambered swim bladder (sb). In situ target strength (TS) measurements on this species are only possible at night, when anchovies disperse and form a scattering layer near the sea surface. A survey data series comprising more than50000 single target detections, recorded from 1995 to 2008, was analyzed in order to study the species specific TS at 38 kHz. The results of this study were recently published at the ICES JMR and a synthesis is presented at RIO Acoustics Symposium given the importance of the several anchovies stocks distributed off South America's coasts. A TS vs. fish total length (L) equation was obtained from the in situ measurements (TS= 31.9 log L − 82.4 dB; R2= 0.78). When the slope of the regression line was forced to 20 into the TS equation, the resulting value for the constant term (b20) was −68.6 dB. In any case, these results indicate an average difference of +3 dB (higher TS values) when compared with the...
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Papers by Adrián Madirolas