Abstract This study compares local ecological knowledge (LEK) of fishers from the Southwest Atlantic Ocean (SWAO), Brazil, related to the franciscana dolphin (Pontoporia blainvillei). We conducted 330 ethnographic interviews in ten fishing communities in southern and southeastern Brazil between 2012 and 2018. Boolean or Classic Logic was used to identify 95 fishers who were able to recognize the franciscana dolphin accordingly to the taxonomic entity P. blainvillei: 23 in northern Espírito Santo state, one in southern Espírito Santo, 20 in northern Rio de Janeiro state, and 51 in northern Paraná state. Among these 95 fishers, 87.4% (n = 83) reported incidental captures in fishing nets. Among these, 52 (54.7%) did not know any solution to this problem. Interviews revealed that the fishers usually discard carcasses in the sea after fat and muscle tissue are removed so that they can be used as bait for shark fishing or as food. In Southeastern Brazil, fishers LEK related to their ability to identify franciscana dolphin varied from ‘no identification’ and ‘extremely low identification’ to ‘partial’ and ‘good identification,’ while in southern Brazil, fishers mainly presented a ‘good identification’ of the dolphins. We propose comanagement actions to conserve the franciscana dolphin in the SWAO.

Abstract This study analyzes the influences of environmental variables on the weight-length relationship of the penaeid shrimp Xiphopenaeus kroyeri during nine consecutive years (2005 to 2013) in northern Rio de Janeiro State. The main questions raised are: i) Does species relative growth vary along time? and ii) How are the environmental variables sea surface temperature, salinity, chlorophyll-a and/or organic matter related to the relative growth? For males, the long-term mean of the allometric coefficient stayed <3 (immature: 2.49; mature: 2.91), whereas for females they were >3 (immature: 3.08; mature: 3.10). The sine-consine models highlighted the wave T period in which the allometric coefficient values complete one cycle of increase-decrease: 4.72 years and 14.72 years for immatures female and male, respectively; and 9.08 years and 9.98 years for matures male and females, respectively. The relative growth behavior varies in a predictable time scale; however, none of the environmental variables strongly supported the variation. Changes in the relative growth behavior are probably drive by intrinsic mechanisms to maintain the population locally.

A transferência trófica de mercúrio total (THg) e sua bioacumulação das espécies de presas para o peixe predador Trichiurus lepturus foi analisada em águas costeiras do sudeste do Brasil para avaliar a dinâmica de elemento traço neste sistema predador-presa. A relação isotópica (δ15N and δ13C) entre o predador e suas presas permitiu inferências sobre a assimilação das presas e os hábitos alimentares do predador. O incremento THg variou de 4,5 a 19,5 vezes entre a presa e o predador, com uma força de biomagnificação de 0,59. As espécies de presas podem ser divididas em três grupos em relação aos valores de δ15N: i) 13,6 a 13,2‰ (juvenis co-específicos, Pellona harroweri e Peprilus paru); ii) 12,5 a 11,8‰ (Chirocentrodon bleekerianus, Lycengraulis grossidens e Dorytheuthis plei); e iii) 10,5‰ (Xiphopenaeus kroyeri). Com base nos valores δ13C, os grupos de presa foram: i) -15.3‰ (X. kroyeri); ii) -17,6 a -16,8‰ (C. bleekerianus, D. plei, P. harroweri, P. paru, e juvenis co-específicos); e iii) -18,7‰ (L. grossidens). Os valores de THg e δ15N destacaram os juvenis co-específicos como a principal via deste elemento traço e a presa mais assimilada. A relação isotópica entre o predador e suas espécies de presas demonstrou uma atividade alimentar preferencialmente costeira e pelágica.

The trophic transfer of total mercury (THg) and its bioaccumulation from prey species to the predator fish Trichiurus lepturus was analysed in coastal waters of southeastern Brazil to evaluate the trace element dynamic in this predator-prey system. The isotopic (δ13C and δ15N) relation between this predator and its prey allowed inferences on prey assimilation and predator feeding habits. The THg increment varied from 4.5 to 19.5 times between prey and predator, with a biomagnification power of 0.59. The prey species could be divided into three groups regarding δ15N values: i) 13.6 to 13.2‰ (juvenile conspecifics, Pellona harroweri, and Peprilus paru); ii) 12.5 to 11.8‰ (Chirocentrodon bleekerianus, Lycengraulis grossidens, and Dorytheuthis plei); and iii) 10.5‰ (Xiphopenaeus kroyeri). Based on δ13C values, the prey groups were: i) -15.3‰ (X. kroyeri); ii) -17.6 to -16.8‰ (C. bleekerianus, D. plei, P. harroweri, P. paru, and juvenile conspecifics); and iii) -18.7‰ (L. grossidens). The values of THg and δ15N highlighted juvenile conspecifics as the main via of this trace element and the most assimilated prey. The isotopic relation between predator and its prey species showed a feeding activity preferably coastal and pelagic.