Are fish ‘Bad Moms’?

By: Dana Sackett

The lives of fish cannot technically be compared to the lives and pressures placed on today’s human moms (that then naturally let loose in an epic party).  However, in honor of Mother’s Day we decided to share some of the maternal roles fish play and imagine if these same roles existed for us humans. 

First off, the primary way fish moms impact their offspring is through their diet and size prior to laying eggs; with larger fish having more and higher quality eggs.  These higher quality eggs are also the individuals that have the best chance at survival.  In fact, most researchers use these maternal traits to help determine the health and future of fish populations. 

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Mom fish typically impact offspring by their size and age.  For instance, a 20-inch red snapper will produce three times as many eggs as a 16-inch red snapper, and a 32-inch red snapper produces 24 times as many eggs as a 16-inch red snapper (Porch et al. 2013). Source

Further, as of 1981, it was estimated that 20% of the then 495 known bony fish families showed parental care.  However, more than half of those cases of parental care were provided exclusively by the males. The remaining 40% of fish that showed parental care involved some form of care from the female. 

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A hilarious human mom’s letter to her child’s future betta fish can be found here: http://experiencedbadmom.com/alettertomysonsbettafish/

This relatively low level of fish parental care, compared to many other vertebrate species, comes down to evolutionary trade-offs.  The theory being that the energy, time, and risk, from expressing aggressive behavior (which could harm the parent), to protect young would only be worth it if those actions dramatically increased the survival and fitness of the offspring.  This means that if the investment in care is not worth it (for example if the chances of offspring survival is low despite parental care, if there is a low number of fertilized eggs, if care could endanger the chances or survival of future offspring) there is a good chance the momma fish will cannibalize her offspring to recover some of the energy expended during spawning. 

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Cichlid with young in the mouth. Source

One form of maternal care in fish is known as mouthbrooding (however, it is important to note that for many fish species it is the male fish that are the mouthbrooders). Mouthbrooding occurs across numerous families of fish and several hundred species of cichlids.  One such cichlid group that have mouthbrooding members and that may be familiar to the common fish consumer is ‘tilapia’.  These cichlid momma fish will begin with incubating fertilized eggs and larvae in the mouth, all the while fasting so as to not eat her offspring.  While in the fish momma’s mouth, she will clean the eggs by sucking away loose particles and churn the young in her mouth to enhance respiration.

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Source

After young are released, the momma fish will frequently still provide care by guarding juveniles and taking them back into her mouth at night or when they are threatened.  The cost of this type of care is high.  Females often lose body mass and condition from not eating and expending energy to protect young.  The lower growth from this fasting can impact the mother’s future reproductive rate. Thus, there is a marked end to care when the female becomes aggressive towards her young and cannibalization can occur.

mouthbrooder-in-the-grass-pic
Source

On the human-end of these comparisons, ‘the larger the female the better,’ and the prevalence of males as primary caregivers would be a nice change of pace for us humans (I do love cake).  Indeed, these traits may even leave some moms, on those more challenging days, wishing for a fish’s life.  However, I can say that I am thankful (and I am sure my children are too) that we human moms do not store our children in our mouth while starving ourselves, then ultimately decide to give up, eat them, and try for another batch of kids when we get ‘h-angry’.

 

Below, share your fun fish mom knowledge or just your funny ‘h-angry’ mom moments in honor of Mother’s Day.  

 

Happy Mother’s Day!

 

References and reading material:

Carter AB, Carton AG, McCormick MI, Tobin AJ, Williams AJ. Maternal size, not age, influences egg quality of a wild, protogynous coral reef fish Plectropomus leopardus. Marine Ecology Progress Series 529: 249-263.

Gittleman JL. 1981. The phylogeny of parental care in fishes. Animal Behavior 29: 936-941.

Gross MR, Sargent RC. 1985. The evolution of male and female parental care in fishes. American Zoology 25: 807-822.

Mrowka W. 1987. Filial cannibalism and reproductive success in the maternal mouthbrooding cichlid fish Pseudocrenilabrus multicolor. Behavioral Ecology of Sociobiology 21: 257-265.

Perrone Jr. M, Zaret TM. 1979. Parental care patterns of fishes. The American Naturalist 113: 351-361.

Porch, C.E., G.R. Fitzhugh, and B.C. Linton.  2013.  Modeling the dependence of batch fecundity and spawning frequency on size and age for use in stock assessments of red snapper in U.S. Gulf of Mexico waters.  National Marine Fisheries Service, Southeast Fisheries Science Center, Miami, Florida.  SEDAR 31-AW report.  20 pp.

Renn SCP, Carleton JB, Magee H, Nguyen MLT, Tanner ACW. 2009. Maternal care and altered social phenotype in a recently collected stock of Astatotilapia burtoni cichlid fish. Integrative and Comparative Biology. 49:660-673.

Saenz-Agudelo P, Jones GP. Mothers matter: contribution to local replenishment is linked to female size, mate erplacement and fecundity in a fish metapopulation. Marine Biology 162: 3-14.

Sato T, Hamano K, Sugaya T, Dan S. 2017. Effects of maternal influences and timing of spawning on intraspecific variations in larval qualities of the Kuruma prawn Marsupenaeus japonicas. Marine Biology 164: 70.

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