Intensive aquaculture can produce yields that are orders of magnitude beyond natural ecosystems How to maximize energy flow to fish Increased nutrient loading—fertilization + ammonia and anoxia tolerant species Shortening the food chain—primary consumers (eg carps, tilapia or mullets) Don’t rely on natural recruitment and managing the life cycle—stocking/hatcheries Increasing consumption efficiency—small pens intensive feeding Increased assimilation efficiency—feeding with easy to digest food pellets Increased production efficiency—low activity species that don’t mind crowding,, highly turbid water

Many aquaculture proponents argue that aquaculture reduces harvesting pressure on wild fisheries. Salmonid aquaculture not very trophically efficient, food pellets made from by-catch of wild species Major water quality issues—nutrientpollution from cages, anti-fouling paint, antibiotics, habitat destruction Transmit diseases to wild salmonids—bacteria, viruses, protozoans, fungi, “fish lice” –parasitic copepods and other Crustacea Genetic problems when domestic escapees compete with or interbreed with wild fish Argulus Lepeophtheirus salmonis

If the productivity of a phytoplankton population is 4000 k J (kilo Joules) /yr / m 2, If sedimentation rate of dead cells to the substrate constitutes 1600 kJ/m 2 yr, and the phytoplankton population is dB/dt=0. If the rain of zooplankton fecal pellets to the bottom is 1400 kJ/m 2 /yr. What is the assimilation efficiency of the zooplankton trophic level (assume that they are all feeding on phytoplankton) or 42% or 60% or 35% or 25% 5.None of these What is the exploitation efficiency EE (or Consumption efficiency CE) of the zooplankton trophic level or 42% or 60% or 35% or 25% 5.None of these

If the net production efficiency of the zooplankton trophic level is 0.40 (40%) what is the ecological efficiency ( ) of the trophic level or 15% or 5% or 10% or 25% 5.None of these If the zooplanktivorous fish are consuming zooplankton at the rate of 400 kJ/yr/m 2, their EE (CE) is or 40% or 60% or 100% or 25% 5.None of these

If the zooplanktivorous fish have an assimilation efficiency of 0.70 (70%) and Net production efficiency (NPE) of 0.20 (20%), the productivity at this trophic level is 1.40 kJ/yr/m kJ/yr/m kJ/yr/m kJ/yr/m 2 5.None of these If in another lake with similar zooplankton productivity the planktivore fish productivity was 2 X higher, a possible explanation for this would be 1.the AE of the fish in that lake was 2X as high 2.the NPE of the fish in that lake was 2X as high 3.the EE (CE) in that lake was 2X as high 4.the AE*NPE in that lake was 2X as high 5.both b and d are true 6.both b and c are true

The standing stock of energy in the plankton is low but it is turned over rapidly, because the organisms are small, grow rapidly and don’t live long A P H1H1 H2H2 Residence time and turnover of energy by trophic levels Turnover is slower at higher trophic levels, since larger organisms accumulate energy over a longer life span—longer residence time and slower turnover Planktonic Herbivore (50  g) life span 1 month Benthic Detritivore (0.1 g) life span 1yr Phytoplankton (0.01  g, life span, few days Carnivorous fish (100g) life span 5-10 yr

Summarizing concepts on Secondary production The organic matter produced by primary producers (NPP) is used by a web of consumers NPP is used directly by primary consumers (herbivores and detritivores), which are in turn consumed by carnivores. Measurement of 2 o Production is done by estimating the rate of growth of individuals and multiplying by the number of individuals per unit area in the cohort (age or size group). The efficiency of secondary production ranges from 5-20% (Avg 10%) at each trophic level. Efficiency depends on several factors--palatability, digestibility, energy requirements for feeding (activity costs)(eg homeotherms vs poikilotherms, other limiting factors eg water, and nutrient quality of food. Trophic efficiency can be represented as the product of CE*AE*PE, each of which is dependent on one or more of the above factors. The yields of many important fisheries depends on a combination of NPP, the length ofthe food chain leading to the fish being harvested, and the efficiency of each step. Many of the species that we harvest or very high in the food chain, so a great deal of NPP is required to support them.