By: Megan LaFollette
In September 2017, Journal of Animal Science published an article investigating the impact of rearing in captivity on spermatogenesis and sperm quality in greater amberjack. The greater amberjack is a valuable fish that could be beneficial in European aquaculture. Unfortunately, the development of this industry has been difficult because of the greater amberjack’s unpredictable reproduction in captivity. Recently it has been shown that greater amberjack reared in sea cages have reduced testis development and an early cessation of spermatogenic activity. This study’s objective was twofold. First, to compare reproductive traits (male germ cell proliferation and apoptosis) in wild and captive-reared great amberjack at difference
phases of reproduction. Second, to assess sperm quality of greater amberjack reared in sea cages.
In this study, a total of 14 wild and 12 captive-reared male amberjack
were examined throughout their reproductive cycle: early gametogenesis (late April to early May), advanced gametogenesis (late May to early June), and spawning (late June to July). Captive-reared fish had been reared at a registered aquaculture facility for 3 years with routine farming practices. At this facility
fish were maintain
in large volume sea cages, at low stocking densities, and excellent water circulation. The fish were fed to apparent satiation and grew throughout the study. Wild fish were caught during routine fishing operations. Between these two groups, researchers compared spermatogonial stem cells, proliferating germ cells, and apoptotic germ cells. For captive reared
amberjack, sperm quality was also assessed using computer-assisted sperm analysis.
Captive-reared male amberjack showed multiple signs of compromised reproductive ability. At the beginning of the reproductive season, it was found that captive reared
male greater amberjack had smaller diameter seminiferous lobules, a precocious and progressive decrease of spermatogonial mitosis, and a high level of apoptosis. At the same time, these captive-reared males had a much higher 17-estradiol plasma concentration. Captive amberjack also had a lower percentage of motile spermatozoa. Throughout the reproductive season
captive amberjack had a decrease in spermatozoa motility duration, velocity, and ATP content (a sperm quality marker). During spawning, captive-reared amberjack had an abnormal increase in sperm concentration and increase
of dead spermatozoa.
Overall, this study demonstrates that greater amberjack are
negatively impacted by captivity especially rearing stress. It is clear that – in order to develop the greater amberjack as a viable candidate in European aquaculture – there is a need to improve rearing and handling procedures. In this study, it is possible that handling and management stress for study sampling could have further deteriorated spermatogenesis. The authors suggest that developing handling procedures for minimizing stress could be particularly beneficial to greater amberjack reproduction.
To view the full article, visit the Journal of Animal Science.