Where can I find a good picture of the LMB male/female internal anatomy when they are not in spawning condition? The text book drawings online are of little help. I want to be able to easily & accurately sex the LMB that I remove from the pond. Is there an easy trick? It is easy to tell a girl cow from a boy cow. I can do that at 100 yds.
Even for the experts, it is not foolproof only through visual examination.
There have been several threads on this topic where the experts have chimed in. Hopefully, someone will drop in with a link to one of the good threads.
Please remember I am asking about the internal anatomy: gutting the fish. I understand the only sure thing with an external exam is the genital tube test.
I read that you said "internal" anatomy and also read that you wanted to use the anatomical info to determine which sex of LMB you wanted to remove from the pond.
I figured your phone changed external to internal!
I have no clue about the internal anatomy. I also do not ever recall a thread on Pond Boss on that topic.
OTOH, you must have excellent surgical skills to examine the fish and then put the ones you like back into the pond!
Not a pro on this but from my years of catching and cleaning, egg development isn't an overnight occurance. There's likely a window post spawn and into summer where the ladies won't have eggs present but it's a window in time. I would guess after the dog days of summer and they start of fall is where egg development starts while there is time to develop the eggs before winter arrives and food resources are available.
My rule of thumb has always been eggs = yellow and female vs lack of them is male.
Completely a rookie guess though. One of the scientists/pros around here could have better info.
1.5acre LMB, YP, BG, RES, GSH, Seasonal Tilapia I subscribe to Pond Boss Magazine
Some info. Lots of genetics and chemical information in the article. BG and other multi spawners have fast gonad development , while LMB are a bit slower as semi-synchronous spawers. Maybe 3 mths +-.
Gene Expression Networks Underlying Ovarian Development in Wild Largemouth Bass (Micropterus salmoides) • Christopher J. Martyniuk, • Melinda S. Prucha, • Nicholas J. Doperalski, • Philipp Antczak, • Kevin J. Kroll, • Francesco Falciani, • David S. Barber, • Nancy D. Denslow • Published: March 20, 2013 • https://doi.org/10.1371/journal.pone.005909 Female teleost fishes show remarkable diversity in reproductive strategies. Some reproductive strategies include continuous and semi-synchronous spawning, sex reversal, and synchronous or simultaneous hermaphroditism. Fish that are fractional spawners develop eggs rapidly for fertilization over relatively short time scales (days to weeks) while synchronous spawning fish develop their eggs gradually over an entire breeding cycle (months). Despite the wide diversity in reproductive strategies, there are characteristic morphological and physiological changes that occur as the oocytes grow and mature. In general, active nuclear transcription and DNA recombination drives meiotic divisions of oogonia during primary growth phases of development. Largemouth bass (LMB) (Micropterus salmoides) are widely distributed throughout the southern continental USA. LMB have significant economic value because they are highly prized in the sport-fishing industry, in addition to being ecologically important as apex predators in their freshwater environments. LMB are semi-synchronous reproducers and many populations in central Florida typically spawn during mid to late spring (end of March-early April) when water temperatures are approximately 75°F. Floridian LMB sampled in mid-late spring have higher gonadosomatic indices (GSI) when compared to individuals sampled in other seasons, and in the summer months Florida LMB are sexually recrudescent, exhibiting little ovarian development [11]–[12]. Adult female and male LMB were collected by electroshocking from October 2005 to April 2007 at Welaka, FL USA (29.48° N, 81.67° W), located approximately 20 miles south of Palatka, FL on the St. John’s River in an area that is considered to be relatively free from the influence of industrial effluent and agricultural runoff Female LMB ovaries were categorized into eight ovarian stages based on histology following the categories described by Grier et al. [13] and used previously by us [12]. The stages included primary growth stages of perinuclear (PN) and cortical alveoli (CA), early vitellogenesis (eVtg), late vitellogenesis (lVtg), early oocyte maturation (eOM), late oocyte maturation (lOM), ovulation (OV), and atresia (AT). The LMB ovary starts out in the fall in the PN state. As environmental temperature decreases, cohorts of oocytes progress through the various stages together, with one cohort leading the way, but followed by additional cohorts of eggs that appear to mature together. Therefore, at any time after the process starts, the ovary is heterogeneous and contains eggs at different stages of development. Oocytes in the PN stage begin to accumulate oil droplets, which marks early transition into pre-vitellogenesis. This transition is predominantly dependent upon water temperature and photoperiod; for LMB populations located in Florida, this begins in early to mid-Autumn. Secondary growth is characterized by the active accumulation of plasma Vtg as well as other nutrients important for growth of the oocytes. Vitellogenesis is marked by active receptor-mediated endocytosis of Vtg and other very low density lipoproteins. Related to these events, notable transcripts with higher expression in secondary growth phases included genes involved in mitochondrial function (cytochrome b and c, NADH dehydrogenase subunit 5). Other regulated genes included cytochrome P450 1A, cholecystokinin, low density lipoprotein receptor (ldlr), and apolipoproteins while some notable transcripts with lower expression during vitellogenesis compared to primary growth stages included follistatin and growth hormone receptor 1.
JECraig - because you are in Florida the egg development of LMB article is very applicable to your FL location. In the article it says "for LMB populations located in Florida, this begins in early to mid-Autumn. Secondary growth is characterized by the active accumulation of plasma Vtg as well as other nutrients important for growth of the oocytes." Thus in FL during winter Dec-Feb evidence of egg mass should usually be fairly evident. No small egg mass then it is very likely your fish is a male. Here is a discussion of eggs in LMB and SMB during October from Michigan waters. Surely LMB in Nov-Dec in FL should have similar sized egg development. https://www.michigan-sportsman.com/threads/bass-with-eggs-in-october.663861/
See this link for a video for internal dissection of a LMB that had early development of an egg mass.
Now my opinion for you is you should be primarily removing LMB during Dec-Feb (maybe Mid-late Nov) and doing a gut removal and examination to best determine gender.
See this link for some visual help where the egg mass is located in the gut cavity for Sm & LMbass. Obviously early in the egg development process the smaller the egg mass. But once the eggs start accumulating yolk material the more yellow the egg mass that develops. If you are not very familiar with internal LMB anatomy see the links to where the developing egg mass is located in relation to the contents of the body cavity. pictures 5 & 10 https://fishpathogens.net/host/smallmouth-bass https://fishpathogens.net/image/p1020183sasmbjpg
If not familiar with body cavity contents of LMB then you will have to do some practice dissections of various LMB during late winter Jan-Feb to see the various locations of the internal LMB egg mass as the winter progresses and egg mass development enlarges toward the spawning cycle. Lack of paired eggs masses usually will indicate a male bass, especially if instead of eggs, there will be an elongated white organ material near where the eggs are usually located in the female. This is the testes of the male.
If your ultimate goal is to remove male LMB, then if it were me, I would be focusing my angling efforts catching nest holding bass during the spawning season. Thus the majority of your fish captured would / should be male when you are fishing shallow areas where LMB are likely to be spawning. Obvious plump bass during the pre-spawn and height of the spawn would be your females.
Last edited by Bill Cody; 11/14/2408:43 PM.
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