ABSTRACT. Four 100 m lengths of both monofilament gill nets and trammel nets were deployed at depths between 15 and 18 m off the coast of the Algarve (south of Portugal) between April 1995 and June 1996. The nets were set on a natural rocky bottom with one end cut loose to simulate lost nets.Changes in net structure (net height, effective fishing area, movement, colonisation, wear and tear) and their catches (species, sizes, numbers, and biomass) were monitored by divers. Similar patterns were observed in all the nets, with a sharp decrease in net height and effective fishmg area, and an increase in visibility within the first few weeks. Net movement was negligible except in the case of interference from other fishing gears. Catch rates were initially comparable to normally fished gd.l nets and trammel nets in this area, but decreased steadily over time. No sea birds, reptiles or mammals were caught in any of the 8 nets. Catches were dominated by fish (89% by number, at least 27 species), in particular by sea breams (Sparidae) and wrasscs (Labridae). Under the conditions experienced throughout the study the fishlng hfetime of a 'lost' net is between 15 and 20 wk. Based on an exponential model, we estimated that 100 m lengths of gill net and trammel net will catch 314 and 221 fish respectively over a 17 wk period.However, we consider this to be an underestimate due to high rates of predation and scavenging by octopuses, cuttlefish, moray eels, conger eels, and other fish such as the wrasse Coris julis. When the nets were surveyed in the following spring. 8 to 11 mo after being deployed, they were found to be completely destroyed or heavily colonised by algae and had become incorporated into the reef.KEY WORDS: Lost gear. Ghost fishing. Gill n e t . Trammel n e t . Catches. Incidental mortality INTRODUCTIONThe impact of lost fishing gear on the environment has aroused considerable concern in recent years (Laist 1995). Of particular concern is the danger posed to rare and endangered species of marine mammals, sea birds and turtles (Degange & Newby 1980, Henderson 1984, Millner 1985, Perrin et al. 1994. It has been estimated that millions of sea birds and thousands of turtles and marine mammals may die each year when entangled or trapped in lost gear (Colema et al. 1983). In commercial fisheries, incidental mortality due to gear over which the fisherman has lost control, may be highly significant (Chopin et al. 1995). 'Ghost fishing' can be defined as the capacity of a fishing gear to continue to fish after it has been lost and the fisherman has lost control. For example, Breen (1987) estimated that ghost fishing traps caught a n amount equivalent to 7 % in weight of the reported commercial catch of Dungeness crab. Similarly, lost fish traps were estimated to catch a quantity equivalent to 3-13.5% of the total Kuwait landings (Mathews et al. 1987), and the decline in Gulf of St. Lawrence Queen crab has been partially attributed to mortality associated with lost crab traps (Blois 1992).In addition to being a source...

Trawling is the most common method of shrimp harvesting. This technique causes a negative impact on the fauna due to the high bycatch rates and to the animals that are accidentally caught and generally returned to the sea dead. The consequences of this technique and the biological aspects of the involved species are poorly studied, specially in the Brazilian northeast. The objective of this study was to show some aspects of the population biology of Isopisthus parvipinnis (Bigtooth corvina) captured as bycatch during sea-bob (Xiphopenaeus kroyeri) shrimp fishing in the region of Ilhéus, in the state of Bahia in Brazil. A total of 1290 individuals were caught in a monthly sampling at three different stations, from March, 2003 to February, 2005. The standardized Morisita index of dispersion suggests that this species has a clumped distribution in the studied area. The number of individuals showed a significant variation (p < 0.0001) between the seasons, being higher during the winter. The estimated first maturation length (L 50 ) was about 159 mm, and 95% of the captured individuals were below this value. The sexual ratio found was 1.5 males for each female. Concerning to diet, 10 feeding categories were identified, and Decapoda Dendobranchiata was the most important in numeric frequency and occurrence. This fact suggests that Isopisthus parvipinnis is a carnivorous species, with a tendency toward crustacean-eating at least in the younger individuals.A pesca de arrasto é o método mais comum de captura de camarão. Esta técnica causa impactos negativos na fauna demersal devido ao grande número de animais que são capturados acidentalmente e que geralmente são devolvidos mortos ao mar. As conseqüências desta metodologia de pesca e os aspectos biológicos das espécies envolvidas são pouco estudados, especialmente no Nordeste do Brasil. Este estudo tem como objetivo mostrar aspectos biológicos de Isopisthus parvipinnis (tortinha) capturada como fauna acompanhante da pesca do camarão sete barbas (Xiphopenaeus kroyeri) na região de Ilhéus, no estado da Bahia, Brasil. Um total de 1290 indivíduos foram capturados em coletas mensais, em três pontos de coleta distintos, de março de 2003 a fevereiro de 2005. O índice de dispersão de Morisita padronizado sugere que a espécie, na área analisada, apresenta uma distribuição agregada. O número de indivíduos variou significativamente entre as estações do ano (p < 0,0001), sendo maior durante o inverno. O comprimento estimado de primeira maturação (L 50 ) foi de 159 mm, sendo que 95% dos indivíduos capturados estavam abaixo deste valor. A razão sexual encontrada foi de 1,5 machos para cada fêmea. Quanto à dieta, foram identificadas 10 categorias alimentares, sendo que Decapoda Dendobranchiata foi a mais importante em freqüência numérica e de ocorrência. Este fato sugere que Isopisthus parvipinnis é uma espécie carnívora, com tendência a carcinofagia, ao menos nos indivíduos jovens.

Resumen.-Larimus breviceps, Isopisthus parvipinnis y Paralonchurus brasiliensis son las 3 especies de Sciaenidae más abundantes en la Reserva Extractiva Marina de Corumbau, en Bahia, nordeste de Brasil. Se analizaron los cambios ontogenéticos y estacionales en las dietas de estas especies. Estos cambios pueden reflejar las adaptaciones y mecanismos de coexistencia utilizados por estas especies. El muestreo se llevó a cabo entre diciembre 2007 y septiembre 2008 con arrastreros. Los peces y las gambas fueron los principales recursos consumidos por estas 3 especies. Para L. breviceps y P. brasiliensis, Sergestidae fue el alimento dominante (junto con poliquetos para el segundo), mientras que los peces fueron el elemento más importante para I. parvipinnis. Se observaron valores bajos de amplitud de nicho para todas las especies. El Índice de Similitud de Morisita indicó baja superposición entre las dietas de las 3 especies en la mayoría de las estaciones del año, a excepción de L. breviceps y I. parvipinnis, que mostraron valores superiores al 80% en todas las estaciones, excepto en verano. Aunque estas especies mostraron diferencias en la posición y orientación de su boca, esencialmente utilizan los mismos recursos. El hábito de alimentación carnívoro, principalmente carcinófago, prevaleció entre los Sciaenidae estudiados.Palabras clave: Hábitos de alimentación, coexistencia, superposición de nicho, amplitud de nicho, nordeste de Brasil Abstract.-Larimus breviceps, Isopisthus parvipinnis, and Paralonchurus brasiliensis are the 3 most abundant species of Sciaenidae in the Marine Extractive Reserve of Corumbau in Bahia (northeastern Brazil). Ontogenetic and seasonal changes in the diet of these species were analyzed. These changes may reflect adaptations and coexistence mechanisms used by those species. Sampling took place between December 2007 and September 2008 with otter trawlers. Fishes and shrimps were the main resources consumed by these 3 species. For L. breviceps and P. brasiliensis, Sergestidae was the dominant food item (together with polychaetes for the latter) and fishes were the most important item for I. parvipinnis. Low values of niche breadth were observed for all species. The Morisita Similarity Index indicated a general pattern of low overlap between the diets of the three species analyzed in most of the seasons, with the exception of L. breviceps and I. parvipinnis, which showed values higher than 80% in all seasons, with the exception of summer. Although these species showed differences in the position and orientation of their mouth, they essentially use the same resources. The carnivorous feeding habit prevailed among the studied Sciaenidae, with predominance of the carcinophagous habit.