Investigating food limitations in wild fisheries: Estuarine fish form dynamic aggregations around a supplementary feeding station and increase localised secondary productivity

2021 ◽  
pp. 105527
Author(s):  
Denham G. Cook ◽  
Peter Jaksons ◽  
Maryam Alavi ◽  
Alistair Jerrett
Keyword(s):  
Supplementary Feeding ◽  
Estuarine Fish ◽  
Feeding Station ◽  
Secondary Productivity

Crocodilians and fisheries in the Philippines: revisiting Fittkau’s hypothesis

2020 ◽  
Vol 14 (2) ◽  
Keyword(s):  
Primary Productivity ◽  
The Philippines ◽  
Estuarine Fish ◽  
Confounding Factors ◽  
Fishing Pressure ◽  
Catch Per Unit Effort ◽  
Fish Catch ◽  
Crocodylus Porosus ◽  
Secondary Productivity ◽  
Palawan Island

Crocodilians have been assumed to influence aquatic primary productivity and fishery yield. However, strong empirical evidence to support such claims is lacking. The long-standing assumption first hypothesized by Fittkau (1970), is that local fisheries (secondary productivity) in areas inhabited by crocodilians would be expected to improve. We tested this hypothesis at two locations in the Philippines, inhabited by the Philippine Crocodile (Crocodylus mindorensis) in Paghungawan Marsh in Siargao Island Protected Landscape & Seascape (SIPLAS), Jaboy, Pilar, Surigao Del Norte, and the Indo-Pacific Crocodile (Crocodylus porosus) in the Rio Tuba River, Bataraza, southern Palawan Island. Water chemistry parameters, with emphasis on nutrient (nitrate and phosphate) levels, were determined using using standard protocols. Catch-per-Unit Effort (CPUE) of gillnets in sites with crocodiles was compared with corresponding control sites without crocodiles. CPUE was higher in areas inhabited by crocodiles, but appeared not to be directly influenced by nutrient levels. Increased fish catches in areas inhabited by crocodiles might be attributed to several factors, such as reduced fishing pressure due to the presence of crocodiles which discouraged the local fishermen to fish intensively. Overall, while fish catch was higher in areas inhabited by crocodiles, it is too early to attribute this to the nutrient output from crocodiles due to several confounding factors. KEYWORDS: estuarine, fish catch, freshwater, nutrient

Variation in the wheat intake of individual sheep measured by use of labelled grain: behavioural influences

1981 ◽  
Vol 21 (111) ◽  
pp. 395 ◽  
Author(s):  
E Juwarini ◽  
B Howard ◽  
BD Siebert ◽  
JJ Lynch ◽  
RL Elwin
Keyword(s):  
Dominance Hierarchy ◽  
Tritiated Water ◽  
Supplementary Feeding ◽  
Previous Experience ◽  
Feed Consumption ◽  
Wheat Grain ◽  
Accurate Calculation ◽  
Early Introduction

A preliminary experiment with sheep in pens demonstrated that wheat grain could be labelled with tritiated water so that when fed it could provide data that would allow accurate calculation of individual feed consumption. This techinque was used with two groups of sheep fed supplementary wheat grain in paddocks. Half of the animals had previous experience of grain feeding some eight months earlier and the others had not eaten grain. Individual diversity of intake could be estimated usefully by tritium labelling of wheat, which was fed to the sheep in a group. The experiment showed that there was a threefold difference in the amount of wheat eaten between the lowest and highest intakes. Further, animals with previous experience of grain feeding consumed the entire ration initially, but those without previous experience did not consume all of the ration until two weeks after wheat feeding began. Over the period of measurement the experienced sheep consumed about 13% more wheat than the non-experienced group. There were insufficient aggressive acts to establish a dominance hierarchy in either group, although the experienced sheep were more aggressive than the others. Aggressiveness by one sheep towards other sheep did not result in higher wheat intakes by the former compared with other sheep in the group. The results are discussed in terms of the variability in acceptance of such supplements by animals, and of the value, later in life, of early introduction of supplementary feeding.

Seasonal dynamics in the exploitation of natural carcasses and supplementary feeding stations by a top avian scavenger

2021 ◽  
Author(s):  
Volen Arkumarev ◽  
Dobromir Dobrev ◽  
Anton Stamenov ◽  
Nikolay Terziev ◽  
Atanas Delchev ◽  
...  
Keyword(s):  
Seasonal Dynamics ◽  
Supplementary Feeding

Optimization of the salmonid nursery stream

1974 ◽  
Vol 31 (11) ◽  
pp. 1827-1837 ◽  
Author(s):  
J. H. Mundie
Keyword(s):  
Food Production ◽  
Supplementary Feeding ◽  
Organic Enrichment ◽  
Productive Capacity ◽  
Fish Food ◽  
Vegetation Control ◽  
Natural Stream ◽  
Discharge Temperature ◽  
Pool Area ◽  
Inorganic And Organic

The minimum unit of the environment containing the essential processes of smolt production is identified as a riffle–pool sequence at a meander. Optimization for smolt rearing is seen to lie through control of discharge, temperature, food production, and cover. The pathways of food production are traced. Ways of increasing the stock of fish-food organisms include adjustment of the ratio of riffle to pool area, choice of streamside vegetation, control of light to the stream, and inorganic and organic enrichment. Ways of making food available to fry include collecting drifting invertebrates at night and releasing them in the day, dislodgement of benthos, attracting aerial insects by lights, and supplementary feeding with artificial foods. None of these procedures, when applied to a natural stream, seems economically feasible. When applied, however, to channels made alongside streams and stocked by the parent stream, they should combine some desirable features of rivers with the productive capacity, but not the costs, of hatcheries.

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