Preliminary Assessment of Age and Growth of the Red Swamp Crayfish Procambarus clarkii [Girard, 1852] in the River Nile in Egypt by Direct and Indirect Methods
Bibliographic record
Abstract
The red swamp crayfish (Procambarus clarkii) is an exceptionally invasive species introduced into the Egyptian freshwater ecosystems in the 1980s for aquaculture purposes. Despite its ecological and economic significance, the age distribution of this species has not been assessed properly using an accurate method. This study is the first to validate the use of growth band counts in the mesocardiac ossicles as a direct technique for age determination in P. clarkii using 166 known-age individuals reared under various temperature regimes. The findings confirm that band counts represent age rather than number of molts. Field comparisons between northern (Giza) and southern (Aswan) Nile populations revealed maximum longevities of six and seven years, respectively, using direct methods, while indirect size–frequency analysis underestimated age at three years. Growth rates were higher at 25 °C compared to 32 °C, both in the lab and in situ. Males matured at larger sizes than females, though age at sexual maturity averaged one year in both regions. This study demonstrates the superiority of direct aging over traditional indirect aging methods, offering critical insights for managing crayfish populations and ensuring sustainable fisheries in the River Nile in Egypt.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".