What is different in the biology of a benthivore like black drum compared to a piscivore like striped bass that can make a black drum healthy on a low lipid diet and a striped bass unhealthy on the same diet?
**Benthivores like black drum (*Pogonias cromis*) are adapted to lower-lipid, protein-rich invertebrate prey and the associated digestive/metabolic physiology, while piscivores like striped bass (*Morone saxatilis*) are adapted to higher-lipid fish prey and depend more on dietary lipids for energy and essential fatty acids.**
### Natural diet and prey composition
Black drum are primarily benthic feeders (mollusks such as clams/oysters, crabs, shrimp, polychaetes, and other invertebrates). These prey are generally lower in total lipid (often ~1–5% wet weight or less, with more structural lipids, protein, and sometimes chitin/exoskeleton material) and have different fatty-acid profiles than forage fish.
Striped bass are primarily piscivorous (especially as larger juveniles/adults), consuming forage fish that are typically higher in storage lipids (triacylglycerols) and n-3 highly unsaturated fatty acids (HUFAs such as EPA and DHA). This creates a higher natural energy density and different macronutrient balance in their diet.
These long-term dietary differences drive physiological adaptations.
### Key biological differences
– **Energy metabolism and protein-sparing**: Piscivores often use dietary lipid preferentially as an energy source so that protein can be directed toward growth (protein-sparing effect). On a low-lipid diet, striped bass tend to increase protein catabolism for energy. This can reduce growth efficiency, elevate nitrogenous waste, and contribute to poorer condition or health issues if energy intake is inadequate. Benthivores are more accustomed to meeting energy needs largely from protein (and whatever modest lipids are available in invertebrates) and can remain healthier when lipid is restricted, provided protein and overall energy are sufficient.
– **Digestive physiology and gut morphology**: Relative intestine length is typically shorter in strict piscivores and longer in invertivores/benthivores. Longer guts support more thorough digestion and extraction of nutrients from lower-energy or more refractory prey (including invertebrate tissues). Enzyme profiles also differ: benthivores often show adaptations for proteases and enzymes that handle invertebrate components (including some chitinase activity), while piscivores are optimized for high lipase activity suited to fish oils and rapid processing of high-lipid meals. Lipid digestibility and lipase characteristics can vary with trophic habit (e.g., differences between bile-salt-dependent carboxyl ester lipases common in many marine carnivores versus other lipase types).
– **Essential fatty acid (EFA) requirements and utilization**: Both species are marine and have limited ability to elongate/desaturate shorter-chain polyunsaturated fatty acids into the long-chain HUFAs they need (EPA, DHA, and often arachidonic acid). They therefore require preformed dietary HUFAs. However, because a “low-lipid” diet supplies less total lipid, the absolute amount of HUFAs delivered is lower. Striped bass (and hybrids) appear more sensitive to insufficient n-3 LC-PUFA and overall lipid energy; performance often improves with adequate fish oil or HUFA supplementation. Related sciaenids such as red drum also require dietary HUFAs (~0.5% of diet or ~7–10% of dietary lipid in classic studies) and efficiently use lipid for energy, but they can perform adequately across a broader range of moderate lipid levels when EFAs are met. Black drum, adapted to lower-lipid invertebrate diets, appear more tolerant of lower total dietary lipid as long as the limited lipid present supplies essential fatty acids.
– **Metabolic rate, activity, and energy density needs**: Striped bass are more active, pelagic/pursuit predators with higher routine and post-prandial energy demands. They benefit from calorically denser (higher-lipid) feeds. Black drum are more benthic/foraging feeders whose natural prey already constrain energy density; their physiology is tuned to extract what is available from lower-lipid meals without the same degree of metabolic stress.
### Practical outcome on a low-lipid diet
A low-lipid formulated diet that still meets protein and minimal EFA needs can support healthy growth and condition in black drum because it more closely matches their evolutionary diet and digestive/metabolic machinery. The same diet is more likely to produce suboptimal growth, poorer feed conversion, increased protein catabolism, tissue fatty-acid imbalances, or other signs of energy/EFA insufficiency in striped bass.
These patterns are consistent with broader trophic differences in fishes (piscivores vs. invertivores/benthivores) in intestine morphology, enzyme profiles, preferred macronutrient ratios, and lipid utilization. Closely related aquaculture species such as red drum illustrate efficient lipid use when available but tolerance of moderate-to-lower lipid levels when EFAs are supplied—aligning with the benthivore/sciaenid side of the comparison. Exact quantitative lipid requirements still depend on diet formulation details (protein level, energy density, specific fatty-acid profile, life stage, temperature, etc.), but the core biological distinction traces to prey-driven adaptations in digestion, energy partitioning, and EFA handling.
Thank you. Could you please give me some more sources for the above information with links?
Here are additional solid sources (with direct links) that support the key points from the previous explanation. I’ve grouped them by topic for clarity.
### Black drum as a benthivore / natural diet (low-lipid invertebrate prey)
– Rubio et al. (2018). Dietary composition of black drum *Pogonias cromis* in a hypersaline estuary reflects water quality and prey availability. *Journal of Fish Biology*.
[https://onlinelibrary.wiley.com/doi/abs/10.1111/jfb.13654](https://onlinelibrary.wiley.com/doi/abs/10.1111/jfb.13654)
(Stomach contents and stable isotopes show heavy reliance on bivalves.)
– Blasina et al. (2010). Trophic ecology of the black drum, *Pogonias cromis* (Sciaenidae), in Mar Chiquita coastal lagoon (Argentina). *Journal of Applied Ichthyology*.
[https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1439-0426.2010.01459.x](https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1439-0426.2010.01459.x)
(Benthic predator focused on bivalves and crabs.)
– Wikipedia summary of feeding (with references): adults primarily mollusks and crabs. [https://en.wikipedia.org/wiki/Black_Drum#Feeding](https://en.wikipedia.org/wiki/Black_Drum#Feeding)
– Additional diet study (Texas / Baffin Bay context):
[https://tamucc-ir.tdl.org/items/8483d179-7a1d-4f82-8ec6-01698696dfbb](https://tamucc-ir.tdl.org/items/8483d179-7a1d-4f82-8ec6-01698696dfbb)
### Striped bass / hybrid striped bass lipid and essential fatty acid requirements
– Nematipour & Gatlin (1993). Requirement of hybrid striped bass for dietary (n-3) highly unsaturated fatty acids. *The Journal of Nutrition*.
[https://jn.nutrition.org/article/S0022-3166(23)00888-X/abstract](https://jn.nutrition.org/article/S0022-3166(23)00888-X/abstract)
(Classic quantification of n-3 HUFA needs; ~1% of diet or ~20% of dietary lipid.)
– Trushenski et al. / related work on fish-oil sparing and LC-PUFA demand in hybrid striped bass (example): [https://www.researchgate.net/publication/292337525_Hybrid_striped_bass_feeds_based_on_fish_oil_beef_tallow_and_eicosapentaenoic_aciddocosahexaenoic_acid_supplements_Insight_regarding_fish_oil_sparing_and_demand_for_-3_long-chain_polyunsaturated_fatty_](https://www.researchgate.net/publication/292337525_Hybrid_striped_bass_feeds_based_on_fish_oil_beef_tallow_and_eicosapentaenoic_aciddocosahexaenoic_acid_supplements_Insight_regarding_fish_oil_sparing_and_demand_for_-3_long-chain_polyunsaturated_fatty_)
– USDA ARS summary on essential fatty acid requirement of sunshine bass relative to dietary lipid level:
[https://www.ars.usda.gov/research/publications/publication/?seqNo115=152461](https://www.ars.usda.gov/research/publications/publication/?seqNo115=152461)
– Recent protein-to-lipid ratio work on striped bass:
[https://link.springer.com/article/10.1007/s10499-024-01639-5](https://link.springer.com/article/10.1007/s10499-024-01639-5)
### Related sciaenid (red drum) lipid / EFA data (useful proxy for black drum family)
– Lochmann & Gatlin (1993). Essential fatty acid requirement of juvenile red drum (*Sciaenops ocellatus*). *Fish Physiology and Biochemistry*.
[https://link.springer.com/article/10.1007/BF00004370](https://link.springer.com/article/10.1007/BF00004370)
(or PubMed: [https://pubmed.ncbi.nlm.nih.gov/24202780/](https://pubmed.ncbi.nlm.nih.gov/24202780/))
(~0.5% n-3 HUFA of diet needed.)
– Effects of dietary lipid levels on red drum growth and body composition: [https://link.springer.com/article/10.1023/A:1007843420128](https://link.springer.com/article/10.1023/A:1007843420128)
### Gut morphology / trophic differences (piscivores vs invertivores/benthivores)
– Diet and habitat as determinants of intestine length in fishes (2024 global analysis). *Reviews in Fish Biology and Fisheries*.
[https://pmc.ncbi.nlm.nih.gov/articles/PMC11297901/](https://pmc.ncbi.nlm.nih.gov/articles/PMC11297901/)
(or [https://link.springer.com/article/10.1007/s11160-024-09853-3](https://link.springer.com/article/10.1007/s11160-024-09853-3))
(Piscivores have the shortest relative intestines among faunivores; invertivores longer.)
– Supporting phylogenetic/trophic patterns: [https://pmc.ncbi.nlm.nih.gov/articles/PMC8495780/](https://pmc.ncbi.nlm.nih.gov/articles/PMC8495780/)
These papers collectively document the dietary differences (invertebrates vs fish), the higher reliance of moronids (striped bass group) on dietary long-chain n-3 HUFAs and adequate lipid energy, the more moderate lipid/EFA needs documented in related sciaenids, and the general pattern of shorter guts in piscivores versus longer guts in invertivores. Direct head-to-head low-lipid feeding trials comparing black drum and striped bass are scarce, so the argument rests on these ecological, morphological, and nutritional datasets.
Let me know if you’d like PDFs where available, more specific aspects (e.g., enzyme data), or help accessing any of these.