A model to estimate the annual production of roes (avgotaracho) of flathead mullet (Mugil cephalus) based on the spawning migration of species

2005 ◽  
Vol 75 (1-3) ◽  
pp. 138-148 ◽  
Author(s):  
George Katselis ◽  
Constantin Koutsikopoulos ◽  
Yiannis Rogdakis ◽  
Thanasis Lachanas ◽  
Evagelos Dimitriou ◽  
...  
2018 ◽  
Vol 69 (3) ◽  
pp. 385 ◽  
Author(s):  
John Stewart ◽  
Anne-Marie Hegarty ◽  
Caitlin Young ◽  
Ashley M. Fowler

Understanding mechanisms supporting the resilience of exploited fish populations is fundamental to sustainable management. Herein we identify sex-specific differences in life history traits that confer resilience in the heavily exploited population of Mugil cephalus along eastern Australia. M. cephalus in this region emigrate from estuaries and undergo an annual northerly spawning migration that is dominated by males. Males mature, on average, at younger ages than females and were most abundant in the spawning migration at age-4, whereas females were most abundant at age-5. Females grew significantly faster and larger than males, with both sexes being aged up to 14 years. These sex-specific differences relate directly to the population stability of M. cephalus under the reproductive strategy of a spawning migration. Males participate in the spawning migration at younger ages and in greater numbers than females to ensure a sufficient number of males for successful spawning. Females partition more energy to growth than males, maturing and participating in the spawning migration at older ages and larger sizes. The larger body size of females is related to increased fecundity, increased survivorship and more efficient swimming ability. These traits, combined with population strategies of both delayed and skipped spawning, convey substantial resilience.


Author(s):  
G.J.Rys I.M. Ritchie ◽  
R.G. Smith ◽  
N.A. Thomson ◽  
G. Crouchley ◽  
W. Stiefel

The performance of 'Grasslands Matua' prairie grass (Bromus catharticus) was compared with perennial ryegrasses under mowing or grazing in three trials conducted in the southern North Island. Production of Matua under mowing at Flock House and Waimate West was 13% and 19% greater than G.4708 and Nui ryegrass, respectively, with the extra production contributed in summer and winter. At Masterton no difference between Matua and Ariki ryegrass production occurred under grazing. A 31% increase in annual production was recorded for both Matua and G.4708 swards receiving N, compared with those sown with white clover, with the annual yield of G.4708 receiving N similar to Matua receiving no N. Less frequent defoliation increased production of Matua swards by 17% and the Matua component by 38%. Production of Nui in comparison with Matua swards was 14% lower under frequent and 9% lower under infrequent defoliation. Similar production was recorded from red clover under frequent, and infrequent defoliation for both Nui and Matua swards. A 48% lower yield of white clover occurred under infrequent defoliation of Matua swards. At Masterton a higher incidence of goitre in newborn lambs, accompanied by a 12% lower lamb liveweight at weaning, occurred on Matua- compared with Ariki-based swards. Aspects of seasonal production, fertility response, management, and animal health are discussed.


This study concentrated on the assessment of the prevailing parasitic fish diseases in some marine fishes at Ismailia province and how to control the infestation using microalgae. This study was carried out on 1080 pre-mature fish (360 D. labrax (225±25 g) and 360 S aurata (150±25 g) and 360 M. cephalus (125±25 g) collected from similar ponds of studies to be examined at the end of treatment. In addition to that we followed non-treated fish (1080 premature). The infested fish showed dark colour and respiratory signs. Post mortem lesions were a presence of congestion or paleness and destruction of gill filaments. The total prevalence of infestation was the total prevalence of parasitic infection of non-treated fishes was 45.83 %. The highest percentage was in D. labrax 56.94 % followed by S. aurata 47.22%, the lowest percentage in M. cephalus 33.33. The total prevalence of parasitic infection in premature treated with 2 g algae was 28.79%, followed by 3 g algae was 23.60 %, while the lowest percentage with 5 g algae was 20.37 % respectively. The detected species of parasites were protozoal parasites, Amyloodinium ocellatum and Riboscyphidia in additions of marine monogenea, Lamellodiscus diplodicus isolated from D Labrex, Mugil Cephalus and S aurata. The present study concluded that, the use of microalgae instead of fish meal decreased parasitic infestation in marine fish. The histopathological alteration of natural infested examined fishes was also recorded.


1958 ◽  
Vol 36 (8) ◽  
pp. 833-838 ◽  
Author(s):  
J. D. Wood

The non-protein nitrogenous constituents of muscle of migrating sockeye salmon were investigated. These constituents were found to be the same in both male and female fish and were present in approximately the same amounts in both sexes. The histidine content of the muscle in all fish decreased to one fifth of the original value during the early stages of the migratory journey and remained at the low level thereafter. Some of the other constituents changed to a smaller extent, usually increasing in the later stages of the migration. This was especially noticeable in female fish. However, the increase in the concentration of these constituents in the muscle was due to a decrease in the amount of muscle in the fish rather than to an increase in the amounts of the compounds themselves.


Aquaculture ◽  
2021 ◽  
Vol 536 ◽  
pp. 736418 ◽  
Author(s):  
Sandra Ramos-Júdez ◽  
François Chauvigné ◽  
Wendy Ángela González-López ◽  
Hanna Rosenfeld ◽  
Joan Cerdà ◽  
...  
Keyword(s):  

Sign in / Sign up

Export Citation Format

Share Document