Modelling recovery of Celtic Sea demersal fish community size-structure

The Large Fish Indicator (LFI) is a size-based indicator of fish community state. The indicator describes the proportion by biomass of a fish community represented by fish larger than some size threshold. From an observed peak value of 0.49 in 1990, the Celtic Sea LFI declined until about 2000 and then fluctuated around 0.10 throughout the 2000s. This decline in the LFI reflected a period of diminishing ‘large’ fish biomass, probably related to high levels of size selective fishing. During the study period, fishing mortality was maintained at consistently high values. Average biomass of ‘small’ fish fluctuated across the whole time series, showing a weak positive trend in recent years. Inter-annual variation in the LFI was increasingly driven by fluctuation in small fish biomass as large fish biomass declined. Simulations using a size-based ecosystem model suggested that recovery in Celtic Sea fish community size-structure (LFI) could demand at least 20% reductions in fishing pressure and occur on decadal timescales.

Global mitochondrial DNA phylogeography and population structure of the silky shark, Carcharhinus falciformis

Globally, sharks are under enormous pressure from fishing efforts. One such species is the silky shark, Carcharhinus falciformis, which occurs in all the Earth’s tropical oceans and is captured in large numbers in pelagic fisheries. Regionally, the silky shark is listed as Vulnerable to Near Threatened by the International Union for the Conservation of Nature due to high levels of direct and by catch exploitation. Despite major conservation concerns about this species, little is known about its genetic status and level of demographic or evolutionary connectivity among its regional distributions. We report a genetic assessment of silky sharks sampled across a major portion of the species’ global range. We sequenced the complete mitochondrial DNA control region from 276 individuals taken from the western Atlantic and Indo-Pacific Oceans and the Red Sea. Overall, haplotype and nucleotide diversities were relatively large (0.93 ± 0.01 and 0.61 ± 0.32 %, respectively). Nucleotide diversity in Indo-Pacific sharks, however, was significantly lower and about half that in Atlantic sharks. Strong phylogeographic partitioning occurred between ocean basins. Furthermore, shallow but significant pairwise statistical differentiation occurred among most regional samples within the Indo-Pacific, but not the western Atlantic. Overall, at least five mitochondrial DNA populations of silky sharks were identified globally. Despite historically large population sizes, silky sharks appear to be isolated on relatively small spatial scales, at least in the Indo-Pacific, indicating that conservation and management efforts will need to be exerted at relatively small scales in a pelagic and highly vagile species.

Trends in deep-water shark fisheries in the Azores

Deep-sea resources have been increasingly exploited, and due to that, several ecosystems and species have been considerably affected. Deep-water sharks populations have been of the most disturbed by practices of unselected fisheries, bycatch and discard, mainly due to their low commercial value. Those practices make deep-water sharks very vulnerable to overfishing given their life-history traits, increasing their extinction risk. With the prohibition of the direct fishery, and implementation of quotas and TACs (Total Allowable Catches) regarding the deep-sea shark landings, the official landings have dramatically decreased after the 1990s. However, the IUU (Illegal, unreported and unregulated) catch has exponentially increased. With the analysis of catch per unit effort (CPUE), the depths, and the mean weight of the individuals over the years for each one of the nine most caught species in the Azores, we produced a descriptive analysis of the effect of fisheries in those species. The results show that some of these species have been suffering from a great fishing pressure, and their populations will be greatly affected in the near future if drastic measures are not taken when it comes to managing their long term sustainability.

Habitat use and diel vertical migration of bigeye thresher shark: overlap with pelagic longline fishing gear

Pelagic longliners targeting swordfish and tunas in oceanic waters regularly capture sharks as bycatch, including currently protected species as the bigeye thresher, Alopias superciliosus. Fifteen bigeye threshers were tagged with pop-up satellite archival tags (PSATs) in 2012-2014 in the tropical northeast Atlantic, with successful transmissions received from 12 tags for a total of 907 tracking days. Marked diel vertical movements were recorded on all specimens, with most of the daytime spent in deeper colder water (mean depth = 353 m, SD = 73; mean temperature = 10.7 °C, SD = 1.8) and nighttime spent in warmer water closer to the surface (mean depth = 72 m, SD = 54; mean temperature = 21.9 °C, SD = 3.7). The operating depth of the pelagic longline gear was measured with Minilog Temperature and Depth Recorders (TDRs), and the overlap with habitat utilization was calculated. Overlap is taking place mainly during the night and is higher for juveniles. The results presented herein can be used as inputs for Ecological Risk Assessments for bigeye threshers captured in oceanic tuna fisheries, and serve as a basis for efficient management and conservation of this vulnerable shark species.

Habitat predictive modelling of demersal fish species in the Azores

Dissertação de Mestrado, Estudos Integrados dos Oceanos, 25 de Março de 2013, Universidade dos Açores.

Role of the wider Azores region as a nursery ground for North Atlantic blue shark (Prionace glauca)

Tese de Doutoramento, Ciências do Mar (Ecologia Marinha)

Características del subsistema demersal durante el crucero de evaluación del recurso merluza (Cr. BIC SNP-1, 9505-06)

Describe la composición por especies de las capturas obtenidas durante la etapa de evaluación del crucero BIC SNP-1 9505-06, entre el 10 de mayo al 13 de junio de 1995, comprendiendo desde Huarmey hasta Puerto Pizarro. Se capturaron 80 especies entre peces (64), crustáceos (10), moluscos (4), equinodermos (1). La mayor diversidad de especies se encontró al norte de los 6°S (subáreas A, B, C, D); se destaca una disminución hacia el sur de este paralelo.

Características de la estructura especiológica del subsistema demersal durante el invierno de 1996

La fauna acompañante en la pesca de arrastre de la merluza, varía en su composición especiológica, distribución batimétrica, latitudinal y estacional de acuerdo a las condiciones de medio marino. Para el invierno de 1996, se analiza la ocurrencia de la fauna marina de aguas tropicales y templadas, entre Punta Capones y el Puerto de Chimbote durante el Crucero de Evaluación de la Merluza BIC SNP-1 9607-08, empleando una red de fondo tipo Granton 400/127. Se capturaron 69 especies: 56 peces, 4 crustáceos, 5 moluscos, un equinodermo, un cnidario y un cordado. La mayor riqueza íctica se encontró al norte del paralelo 6°S. La captura total en el área estudiada fue de 20.021,43 kg de peces (99%) y 211,24 kg (1%) de invertebrados. La merluza Merluccius gayi peruanus, destaca por su abundancia y frecuencia, se capturaron 18.501,52 kg (91,4% del volumen total). Entre los elasmobranquios, destaca la "raya águila" Myliobatis chilensis y dentro de los teleósteos (peces óseos), los Pisciformes con 19 spp., siendo la familia Sciaenidae la mejor representada con 7 especies.

Variación de la Ictiofauna Demersal frente al Perú entre 1981 y 1987

En la base de datos de cinco cruceros de evaluación de recursos demersales realizados en épocas normales y de El Niño se analizó el número de especies ícticas y el índice de diversidad en relación a la densidad (captura/lance) de los recursos y a las condiciones del ambiente. El número de especies baja de norte a sur y la tasa de reducción se modifica durante los eventos. El Niño en función de la intensidad y duración del fenómeno. La relación entre la densidad (captura/lance), la diversidad y la concentración del oxígeno, se expresa en una ecuación exponencial compuesta.

Estructura del subsistema demersal durante el crucero de evaluación del recurso Merluza, BIC Humboldt 9705-06, Callao a Puerto Pizarro

Presenta la estructura especiológica, distribución, espacio temporal y captura de peces e invertebrados accesibles a redes tipo Granton 130/400 y Engel 998/400, empleadas durante el Crucero de Evaluación del recurso merluza BIC Humboldt 9705-06. Así como el análisis de comunidades de peces del fondo de la fauna acompañante. Se capturó 134 especies: 99 fueron peces, 19 crustáceos, 12 moluscos, 2 equinodermos, 1 cnidario, 1 sipuncúlido y un cordado. En comparación con los dos últimos cruceros BIC SNP-1 9505-06 y 9607-08, la diversidad íctica se incrementó hasta 43%, aún sin haberse constatado presencia de la típica diversidad íctica tropical costera y estuarina. Al sur de los 6°S se encontró distribuida más del 50% de la riqueza íctica. La captura total fue 45.368,59 kg, de los cuales 40.106,04 se obtuvo en 63 lances de fondo y 5.262,55 kg con 20 lances de media agua. El falso volador Prionotus stephanophrys y la merluza Merluccius gayi peruanus fueron las especies más frecuentes y abundantes con 21.259,21 kg y 14.190,51 kg de captura total, respectivamente.

Estructura del subsistema demersal en otoño 2003. Crucero BIC Olaya 0305-06

Se informa sobre la captura y distribución espacial de peces e invertebrados accesibles a la red de arrastre Granton 300/160 utilizada en la segunda etapa del Crucero BIC Olaya 0305-06, del 4 al 17 junio 2003. En 13 días efectivos de pesca con 76 operaciones de arrastre se capturó un total de 21.805 kg de peces e invertebrados. Cuatro especies representaron el 86,8% de esta captura: la merluza, Merluccius gayi peruanus (14.390 kg, 66%); el bereche con barbo, Ctenosciaena peruviana (2.557 kg, 11,7%); el chiri, Peprilus medius (1.235 kg, 5,7%) y la pota Dosidicus gigas (733 kg, 3,4%). Se identificaron 136 especies marinas: 85 peces, 33 crustáceos, 10 moluscos, 6 equinodermos y 2 cnidarios. Esta diversidad fue menor que la encontrada en otoño de los anteriores años 2001 y 2002. En estos tres años sucesivos, la mayor riqueza íctica se encontró al norte de Punta Aguja (6°S), donde se registró entre el 70-92% de las especies, como consecuencia de las condiciones de normalidad en el medio marino.

Estructura del subsistema demersal durante el verano 2004.Crucero BIC Olaya 0401-02.

El Crucero BIC Olaya 0401-02 se efectuó del 14 enero al 7 febrero 2004, de Puerto Pizarro (3°29’S) a Punta Pacasmayo (7°23’S). Se utilizó la red de arrastre Granton 300/160. Se efectuaron 87 arrastres de fondo, la captura total fue 42.015,8 kg, constituida por 169 especies: peces (102), crustáceos (32), moluscos (21), equinodermos (9), cnidarios (4) y anélidos (1). Las especies más importantes fueron: merluza peruana, Merluccius gayi peruanus (31.429,42 kg; 75% del total); bereche con barbo, Ctenosciaena peruviana (2815,67 kg; 6,7%); pota, Dosidicus gigas (1.777,27 kg; 4,2%); lenguado ojón, Hippoglossina macrops (611,82 kg; 1,5%); chiri Peprilus medius (543,67 kg; 1,3%); y el pampanito, Peprilus snyderi (497,54 kg; 1,2%). En conjunto, estas seis especies, representaron el 90% del monto total. Esta diversidad es similar al verano 2003 y también la distribución de los peces, cuya mayor diversidad específica se encontró al norte de Punta Aguja (6°S), indicando condiciones de normalidad.

Studies on food and feeding of marine demersal finfishes with special reference to trophic interactions

Food and feeding habits of fourteen demersal finfishes exploited off the Karnataka coast were studied to investigate trophic interactions within the marine food web. Index of Relative Importance (lRI),Ontogenetic, seasonal (pre-monsoon, monsoon and post-monsoon) variation in feeding and prey-predator relationship studies were conducted.The results of prey-predator trophic interaction studies identified four major trophic guilds based on the predators feeding similarity.Trophic guild I is 'copepod and detritus fceders'with an average group similarity of 61.4%. The second trophic guild, 'prawn and crab feeders'with an average similarity of 52.7%. 'Acetes feeders', the largest trophic guild with an average group similarity of 62.5%, composed of six demersal finfish species.The guild 'piscivores' is constituted by C. limba/us and P. arsius with an average similarity of 45%.For each predator, ontogenetic diet shift is common and is characterized by prey of low to high trophic level.Strong selection of certain prey types was observed in some predators while most of them avoided abundant prey.In addition to Acetes spp, strong predation impact was observed for penaeid prawns, epibenthic crabs and detritus.This information on trophic guilds and prey-predator interactions can be used to construct trophic model on the benthic ecosystem off Karnataka and to investigate fishery induced changes as well as predation impact of different animals on commercially important demersals

Studies on The Larvae of A Few Demersal Fishes of The South West Coast of India

The main objectives of the present study has been the collection of the larvae of some of the important and less studied demersal fishes of the South, West Coast of India, preparation of their life history series, statistical analysis of the morphometric characters, spatial as well as temporal distribution of the larvae in relation to the chief hydrographic parameters such as temperature, salinity and oxygen, so as to delineate the spawning areas and seasons of these fish populations. The informations regarding the kind and amount of bottom fish resources along the Indian Coast are scanty. Even though the flat fish resources of Indian waters contributes a singificant share in the total marine fish landings the detailed studies on biology and fishery have been conducted only for ‘Malabar Sole‘ (Cynoglossus macrostomus) while the reminder species of this group are inadequately known. Lizard fishes (order Myctophiphormes) are always present in the miscellaneous catch in all seasons but an adequate knowledge of the potential resources of this group is wanting. The Bombay duck, coming under the same order, is one of the most heavily fished species particularly along the Maharashtra Gujarat coasts but its early developmental stages are not studied. Hence the present study will contribute to a better understanding of the demersal fishery resources of the South West Coast of India

Fins and Fin Rays from Whale Shark (Rhiniodon typus Smith)

The whale shark (Rhiniodon typus Smith) is an under exploited species and it is mainly caught for its liver oil . The processing of shark fin for rays is reported here . The fins have a high content of rays . The yield of fin rays from undried fins ranged from 0 .53 to 4 .40 percent with maximum ray content in the lower lobe of caudal fin . The physical and chemical characteristics of the rays are reported . The total nitrogen content is about 15 to 16 percent (dry weight basis)