Examination of fine‐scale spatial‐temporal overlap and segregation between two closely related congeners Gadus morhua and Gadus ogac in coastal Newfoundland

Abstract

The spatial and temporal movement patterns of sympatric juvenile Atlantic cod Gadus morhua and Greenland cod Gadus ogac were studied using high-resolution radio-acoustic positioning in a coastal area of Newfoundland during the summers of 2009 and 2010. A total of 20 fish (10 G. ogac and 10 G. morhua) were equipped with acoustic transmitters and monitored for periods up to 23 days. Most fishes showed high site fidelity with mean residence times of 12·4 (G. morhua) and 14·4 days (G. ogac). A few individuals showed a transient use of the study area, ranging distances up to c. 4 km. Mean daily home ranges [95% kernel utilization distributions (KUDs)] and core activity areas were significantly larger for G. morhua (3·8 and 0·5 ha) than for G. ogac (2·7 and 0·3 ha). Home ranges were not related to total length (LT ) for G. morhua but showed a weak positive relationship for G. ogac. Gadus morhua occupied larger areas during the day while G. ogac occupied slightly larger areas at night. Mean rates of movement for G. ogac and G. morhua ranged from 0·83 to 1·24 and 0·76 to 1·76 LT s(-1) , respectively, and were highest during crepuscular periods. Overall, G. morhua were wider ranging, moved at faster rates and were active throughout the diel cycle compared to G. ogac of the same size. It is suggested that differential use of space and activity periods plays an important role in the successful coexistence of these two species.

How to deal with a bad neighbor? Strategies of sympatric freshwater decapods (Crustacea) for coexistence

“…N = 10 per species areas of the stream than P. pilimanus. Although we did not find any marked spatial segregation, unlike that which is reported for some aquatic organisms (e.g., swimming crabs: Guerra-Castro et al, 2007; fish: Louhi et al, 2013;Knickle & Rose, 2014), it is nonetheless clear that the investigated species used the stream differently. Additionally, crayfish remained within their burrows most of the time, avoiding the streambed (Fig.…”

“…Through that, we can infer how different aspects of the environment (i.e., competitors) are shaping how the animal is using the space. Indeed, in ecologically similar fishes, there is evidence that the dominant Atlantic cod possesses larger home ranges and is more active than the subordinate Greenland cod, apparently exploiting the habitat more extensively (Knickle & Rose, 2014). Thus, home range is a reliable measure with which to study how co-occurring species influence each other's space usage, providing us with evidence to infer on adaptations for co-occurrence.…”

“…Therefore, coupling the space use with timing of animal movements in natural environments can help us to elucidate the strategies used to cope with ecological pressures: competing species could choose different microhabitats within the same area, or concentrate their activity in different times (e.g. Knickle & Rose, 2014).…”

Coexistence of Two Closely Related Cyprinid Fishes (Hemiculter bleekeri and Hemiculter leucisculus) in the Upper Yangtze River, China

“…The mechanism that enable species-especially closely related, ecologically similar species-to coexist remains of interest in community ecology [3]. Although similar species commonly coexist in nature, classical niche theory suggests that complete niche overlap is evolutionally impossible [4,5]. Niche segregation, a process by which competing species evolve different patterns of resource-use under evolutionary pressures, is widely used to explain how similar species coexist [6][7][8].…”

“…Rossier [22] confirmed the fish undergo spatial and temporal separation by identifying the spatial (distance from the shore) and seasonal (summer-winter) distributions of the ichthyofauna in the littoral zones of Lake Geneva. Knickle and Rose [5] studied the spatial and temporal movement patterns of sympatric juvenile Gadus morhua and Gadus ogac, using high-resolution radio-acoustic positioning in a coastal area of Newfoundland. Carniatto et al [1] confirmed two sympatric, morphologically similar species of Moenkhausia with segregated food resources.…”