Introduction

1. Organismic Indices and an Autopsy-Based Assessment as Indicators of Health and Condition of FishRonald W. Goede and Bruce BartonAmerican Fisheries Society Symposium8:93-108 (1990)

2. Introduction • Methods that can provide simple and rapid indications of how well fish are coping with their environments are necessary. • Condition indices, particularly indices representative of the whole fish can be used to relate the consequences of biochemical and physiological alterations to observed changes in the individual and the population

3. Purpose • Review the various types of condition indicators that can be used to assess the degree of stress experienced by fish: • Condition factor • Organosomatic Indices • Growth

4. Condition Factor • Weight/length3 • Used to compare growth against established standards • For example, a decline in condition factor is seen when fish are subjected to stress from high rearing density. • A decline in Condition Factor is interpreted as depletion of energy reserves. • Condition factor can fluctuate seasonally, a reflection of feeding activity and nutrient availability. • Condition factor can change with physiological development and sexual maturity.

5. Organosomatic Indices • Ratios of organ weight to body weight • Hepatosomatic (Liver) Index • Drops rapidly during starvation • Can increase following exposure to pollutants or toxins • Due to hyperplasia (increase in cell number) or hypertrophy (increase in cell size) as an adaptive response to increase the capacity of the liver to detoxify foreign compounds. • Viscerosomatic Index (remove food from digestive tract) • Gonadosomatic Index • Splenosomatic Index • Also vary with season, energy availability, sex and life history of the fish.

6. Autopsy Based Condition Assessment • Assumptions • Fish under stress will experience changes in tissue and organ function to maintain homeostasis. • If a change in function exists, there will be a gross change in the structure of organs or tissues. • If the appearance of all organs and tissues is normal, there is a good probability that the fish is normal. • If the appearance of an organ or tissue departs from the normal or from a control condition, the fish is likely responding to changes brought about by the environmental stressor

7. Autopsy Based Condition Assessment • Further Considerations • Environmental stressors may be sufficiently severe that fish die before observable changes in structure or appearance occur. • Microscopic or histological structure changes can occur without gross manifestation. • Comparisons of stressed fish against normal conditions should be based upon fish of the same age, strain, species, sex, and season. • The individual expressing the condition in the sample must be representative of the population.

8. Systematic Approach to the Necropsy/ Goede Index • Collection of Samples • Record weight, length, etc. • Blood Constituents (Lab 4) • Hematocrit (volume of red blood cells per unit volume of whole blood) • Leukocrit (gross measure of white blood cell abundance) • Plasma protein concentration (low plasma protein values are associated with starvation and depletion of energy stores) • Damage to Extremities • Fin/tail erosion, scale loss, etc. • Eyes • Imbalance of fluid or gas pressure may cause exopthalmia • Infections or nutritional disorders may cause cataracts

9. Systematic Approach to the Necropsy/ Goede Index • Gills • May become frayed, clubbed, or pale in color • Pseudobranch • Salt regulating, respiratory, glandular, and sensory organ • Normal appearance is flat or concave • When swollen, it rises above the surrounding skin surface, implying changes in oxygen and CO2 partial pressures. • “Lithic” indicates the presence of mineral deposits • Thymus • Located under the epithelium at the posterior margin of the opercular cavity • Important during young life stages as a lymphoid organ • Indices are based upon the amount of petechial (pin-point) hemorrhaging present

10. Systematic Approach to the Necropsy/ Goede Index • Mesenteric (Visceral) Fat Deposits • Amount present • Spleen • Functions as a blood storage organ and in blood-cell production, as well as disintegration of erythrocytes and the release of hemoglobin. • Condition can be noted as black, red, granular, nodular, or enlarged • Black and Red are considered normal • Hind Gut Inflammation • Indicative of stress-mediated infection from a facultative pathogen or the presence of toxins or other irritants • Kidney • Excretes water from freshwater fish and eliminates magnesium and sulfate ions from marine teleosts. • Head kidney is the primary hematopoietic organ in fish • Nephrocalcinosis appears as white deposits in the kidney

11. Systematic Approach to the Necropsy/ Goede Index • Liver • Glycogen storage, bile production, metabolizes and removes hormones and foreign substances from the blood • Fatty liver condition is attributable to excessive accumulation of fat in the cellular cytoplasm and may be diet related • Nodules and discoloration are likely due to the presence of a pathogen • General discoloration of the liver (blotchy appearance) can occur if a considerable amount of time passes between death and necropsy

12. Systematic Approach to the Necropsy/ Goede Index • Bile • The color of bile in the gall bladder is a good short-term indicator of the feeding activity and nutritional status of fish. • Straw yellow indicates that the fish have been fed within the past couple days • Blue-green pigmentation indicated that the fish has not eaten in a week or longer (oxidation of bilirubin pigments to biliverdin = blue/green color). • Empty gall bladder indicates that the fish have eaten within the past few hours. • State of maturity • Sex and state of maturity of each fish should be recorded because of the possible affects on the extent of mesenteric fat deposition, plasma protein concentration, and other conditions.

13. Health Assessment Index (HAI) • An extension of the field necropsy • Quantative index that allows the comparison of fish populations • Variables are assigned a numerical value based upon degree of severity

14. Fish 424 Laboratory Exercises (Lab 3) Determination of Organismic Indices as Indicators of Fish Health and Condition • Procedure: • Students will perform a necropsy on one population of fish • Take length and weight measurements of the fish • Systematically evaluate your fish and score using the criteria found in Table 1 of Adams et al (1993) and charts handed out in lab. Please use the Substituted Values for HAI, except for Bile and Mesenteric Fat • Record data in your lab notebook and on overhead • Record data from other students • Answer Questions handed out in lab

15. Lab 3 Bile Straw yellow/partially full ----------------------------(0) Yellow/distended --------------------------------------(1) Light to grass green/full ------------------------------(2) Dark green – blue green/ full -----------------------(3) Mesenteric Fat None -----------------------------------------------------(0) Less than 50% of caeca covered with fat -------(1) About 50% of caeca covered with fat ------------(2) Moe than 50% of caeca covered with fat --------(3) Caeca completely covered with fat ---------------(4) Other -----------------------------------------------------(OT)