Discrimination of habitat use between two sympatric species of mullets, Mugil curema and Mugil liza (Mugiliformes: Mugilidae) in the rio Tramandaí Estuary, determined by otolith chemistry

Two sympatric species of marine mullets, Mugil curema and M. liza, use the rio Tramandaí Estuary as nursing grounds. When two closely related species are sympatric, various mechanisms may permit their coexistence, including spatial or temporal segregation that results in the divergent use of the resources for which they compete. To investigate the spatial segregation, we used otolith chemistry inferred through laser ablation-inductively coupled plasma mass spectrometry. Our results indicate that in the rio Tramandaí Estuary, M. curema is associated with high salinity waters and can be classified as a Marine Migrant in the Marine Estuarine-opportunist subcategory. Mugil liza is associated with lower salinity and can be classified as a Marine Migrant in the Estuarine Dependent subcategory. The intra-specific variation in estuarine habitat use indicates that the migratory behaviors in mullets are far more complex than previously known.(AU)

Duas espécies de tainha simpátricas, Mugil curema e M. liza, usam o estuário do Rio Tramandaí como zona de berçário. Quando espécies do mesmo gênero são simpátricas, vários mecanismos podem permitir sua coexistência, incluindo segregação espacial ou temporal que resultam no uso distinto dos recursos pelos quais elas competem. Para investigar a segregação espacial nós usamos a análise de elementos químicos em otólitos inferidos por espectrometria de massas através de plasma indutivamente acoplado com amostras extraídas a laser (LA-ICPMS). Mugil curema está associada a águas de alta salinidade podendo ser classificada como Marinho Migrante sub-categoria Marinha estuarina-oportunista. Mugil liza está associada a águas menos salinas, devendo ser classificada como Marinha Migrante sub-categoria Estuarina Dependente. A variação intraespecífica no uso do habitat estuarino indica um comportamento migratório mais complexo que o previsto em tainhas.

No mullet, no gain: cooperation between dolphins and cast net fishermen in southern Brazil

We report on the interaction between common bottlenose dolphins, Tursiops truncatus (Montagu, 1821) and cast net fishermen in southern coast of Brazil. The fishery was monitored in the mouth of the Tramandaí River Estuary to investigate the seasonality of catches and their relationships with a set of variables: presence/absence and number of bottlenose dolphins, fishing area, temperature, salinity, wind and water flow direction in the channel. The mullet, Mugil liza Valenciennes, 1836 is the target species and was the dominant fish in the catches (77% of total catch; 50% in frequency; 0.2 ind. x f-1). The use of GLM models helped to reveal that the number of the bottlenose dolphins, time of year (months) and spatial variation of fishing activity were the main factors explaining the presence and abundance of mullet in the fishermen’s catches. The presences of bottlenose dolphins in the fishing area raise the probability of fishermen catch larger number of mullets with smaller fishing effort. However, the size of the mullet is influenced basically by seasonality. The mullets are the “currency” of bottlenose dolphins and fishermen interaction. There are reasons for concern about the sustainability of the southern Brazilian M. liza stock, once the decrease of this fishing resource can lead this rare and traditional fishery to the extinction.

Discrimination of habitat use between two sympatric species of mullets, Mugil curema and Mugil liza (Mugiliformes: Mugilidae) in the rio Tramandaí Estuary, determined by otolith chemistry

Two sympatric species of marine mullets, Mugil curema and M. liza, use the rio Tramandaí Estuary as nursing grounds. When two closely related species are sympatric, various mechanisms may permit their coexistence, including spatial or temporal segregation that results in the divergent use of the resources for which they compete. To investigate the spatial segregation, we used otolith chemistry inferred through laser ablation-inductively coupled plasma mass spectrometry. Our results indicate that in the rio Tramandaí Estuary, M. curema is associated with high salinity waters and can be classified as a Marine Migrant in the Marine Estuarine-opportunist subcategory. Mugil liza is associated with lower salinity and can be classified as a Marine Migrant in the Estuarine Dependent subcategory. The intra-specific variation in estuarine habitat use indicates that the migratory behaviors in mullets are far more complex than previously known.(AU)

Duas espécies de tainha simpátricas, Mugil curema e M. liza, usam o estuário do Rio Tramandaí como zona de berçário. Quando espécies do mesmo gênero são simpátricas, vários mecanismos podem permitir sua coexistência, incluindo segregação espacial ou temporal que resultam no uso distinto dos recursos pelos quais elas competem. Para investigar a segregação espacial nós usamos a análise de elementos químicos em otólitos inferidos por espectrometria de massas através de plasma indutivamente acoplado com amostras extraídas a laser (LA-ICPMS). Mugil curema está associada a águas de alta salinidade podendo ser classificada como Marinho Migrante sub-categoria Marinha estuarina-oportunista. Mugil liza está associada a águas menos salinas, devendo ser classificada como Marinha Migrante sub-categoria Estuarina Dependente. A variação intraespecífica no uso do habitat estuarino indica um comportamento migratório mais complexo que o previsto em tainhas.

No mullet, no gain: cooperation between dolphins and cast net fishermen in southern Brazil

We report on the interaction between common bottlenose dolphins, Tursiops truncatus (Montagu, 1821) and cast net fishermen in southern coast of Brazil. The fishery was monitored in the mouth of the Tramandaí River Estuary to investigate the seasonality of catches and their relationships with a set of variables: presence/absence and number of bottlenose dolphins, fishing area, temperature, salinity, wind and water flow direction in the channel. The mullet, Mugil liza Valenciennes, 1836 is the target species and was the dominant fish in the catches (77% of total catch; 50% in frequency; 0.2 ind. x f-1). The use of GLM models helped to reveal that the number of the bottlenose dolphins, time of year (months) and spatial variation of fishing activity were the main factors explaining the presence and abundance of mullet in the fishermens catches. The presences of bottlenose dolphins in the fishing area raise the probability of fishermen catch larger number of mullets with smaller fishing effort. However, the size of the mullet is influenced basically by seasonality. The mullets are the “currency” of bottlenose dolphins and fishermen interaction. There are reasons for concern about the sustainability of the southern Brazilian M. liza stock, once the decrease of this fishing resource can lead this rare and traditional fishery to the extinction.(AU)