The barred grunt Conodon nobilis (Perciformes: Haemulidae) in shallow areas of a tropical bight: spatial and temporal distribution, body growth and diet

Abstract

This study aimed to comprehensively investigate the population biology of Conodon nobilis (Perciformes, Haemulidae) in Caraguatatuba Bight, southeastern Brazil. Monthly trawls were performed from October 2003 through October 2004 in two areas of the bight that are similar to but distant from each other, South and North. For all specimens, the size was measured and the sex and reproductive stage identified. Abundance and size were compared over areas and months. Body growth parameters were parameterized according to the Von Bertalanffy growth function. The stomach contents were identified and quantified. C. nobilis occurred mainly in the North area and showed an erratic pattern of abundance over time. Several cohorts entered in different periods, but very few large and mature individuals were observed. The results indicate a preference for shallow, ocean-influenced habitats and some degree of segregation between young and older individuals. The species showed a distribution consistent with an r-strategist species, with high abundance and a high growth constant (K = 0.68 year -1 and L max = 34.2 cm). Both the relative length of the digestive tube and the prey items indicated a carnivorous feeding habit; mysids were the main item of the diet throughout the study period, indicating that this grunt is a specialist feeder. Other frequently observed items were amphipods and fish fragments. Ingestion of scales is possibly intentional.

Population structure, size at first sexual maturity, and feeding ecology of Conodon nobilis (Actinopterygii: Perciformes: Haemulidae) from the coasts of Pernambuco, north-eastern Brazil

“…In the presently reported study, high FI values were found, indicating an intense use of the environment as a feeding area. Previous studies on the feeding habits of this species Oliveira-Silva 1998, Vasconcelos Filho et al 2010) in Itamaracá Island, northeast part of Brazil and Caraguatatuba Bight, south-eastern Brazil (Pombo et al 2014) have shown that their main prey items are crustaceans. Similar results were observed in the presently reported study, with C. nobilis classified as a zoobenthivore, feeding on crustaceans, mainly shrimps of the family Penaeidae.…”

“…Size differences between months may be related to the level of exploitation in the area, the ecological characteristics of each region, and the differential selectivity of the fishing gear (Frédou et al 2009). Along the southern coast of Pernambuco, the maximum lengths recorded (27.5 cm) for C. nobilis were greater than those recorded for the same species in other areas, e.g., 15 cm in Caraguatatuba Bay, São Paulo (Brazil) (Pombo et al 2014), 12 cm in Rio Grande do Norte (Brazil) (Garcia et al 2010), and 26 cm in the Gulf of Salamanca (Colombia) (Garcia et al 1998). Although the results of the presently reported study may be hampered by the selectivity of the fishing gear, based on the habitat of the species (shallow muddy bottoms) and the L max reported (33.6 cm TL, Cervigón et al 1992), which is near to the range of individuals caught in the presently reported study (6.6 to 27.5 cm TL, including juveniles and adults), we assumed that our sampling adequately covered the size and behaviour of the species, and the parameters provided here are representative of the C. nobilis population in northeast Brazil.…”

“…Conodon nobilis is a benthic carnivorous predator with a short intestine and large stomach that has a great expansion capacity (Garcia et al 2010). Trawls mainly target demersal organisms (McHugh et al 2017) and species that forage near the bottom (Pombo et al 2014), such as C. nobilis, which is directly affected by such trawling activity. The feeding intensity, described as the fullness index (FI), may be greatly influenced by the availability and type of prey, length range of the predator, reproductive season, and daily variation (Pereira et al 2016, Perelman et al 2017.…”

“…Despite being an important food source for local fishers, this species is also an important link in the coastal food web, highlighting the need to understand the role of barred grunt and other species in the ecosystem balance (Garcia et al 2010, Silva-Júnior et al 2019. Although some information on the population dynamics (e.g., diet, population structure, and size at sexual maturity) of the barred grunt is available (Lopes and Oliveira-Silva 1998, Vasconcelos Filho et al 2010, Pombo et al 2014, this essential information does not exist in the region, thereby hampering initiatives of management and conservation of this species.…”

Diet and Feeding Habits of the Javelin Grunt Pomadasys kaakan (Cuvier, 1830) in Pabean Bay West Java

“…Ikan gerot-gerot termasuk dalam Famili Haemulidae yang merupakan jenis ikan demersal dan dinamai grunt karena menghasilkan suara yang berasal dari gesekan gigi dan diperkuat oleh gelembung renang (Pambo et al, 2014). Ciri khas ikan tersebut yaitu: bentuk tubuh pipih, kepala cembung, dagu memiliki dua pori-pori di setiap sisinya yang diikuti dengan lubang yang terletak pada bagian anterior, dan panjang tubuh maksimal 800 mm (McKay, 2001).…”