Hook and Release Mortality Study - YR 3


Year 2010
Proponent Fraser Salmon and Watersheds Program
Project type Fisheries
FSWP funding source Living Rivers
Grant amount $60,000
ID number FSWP10-LR128-F

Location: Lower Fraser, Recreational Bar Fishery

Project Summary

SUMMARY

Estimate short-term (24 hour) sockeye mortality representative of recreational catch and release (C-R) practices that commonly occur in the Fraser River mainstem May to September recreational salmon fisheries.

Assess the influence of selected variables on hooking mortality rates.  This would include as the response variable, dead or alive at the end of the 24-hour holding period, and various predictor variables.

DESCRIPTION

Sockeye will be caught by anglers using a range of gear and angler experience. Handling methods will be representative of Catch and Release (C-R) practices observed during Fraser recreational fisheries in previous years. While the study will include sockeye caught by bottom bouncing and bar fishing techniques, the analysis of a hooking mortality will originate from the pooling of sockeye caught by these collective gears.

Sockeye landed will be individually marked (or tagged), and transported and held in net pens for 24 hours. During the C-R episode and throughout the 24-hour holding period in net pens, all dead fish will be recorded. Dead fish observed in the holding pens will be removed as soon as they are discovered. All fish that are still alive after being held for 24 hours will be released from the net pens into the Fraser River mainstem. A number of variables will be recorded upon capture and throughout the 24-hour holding period (see variables below).

Bars representative (e.g. Grassy Bar and Wellington Bar) of the Fraser River recreational fishery and that occur in close proximity to net pens will be selected.  A total of three long-term (24 hours) holding net pens will be used to provide sufficient space for fish holding and minimize crowding stress; an additional net pen will be used to study short-term (

<4 hours) sockeye response to release in a swift flow area. Volunteer anglers of different ability and experience will be used and gear types will be provided to anglers. For each broad gear type (chinook targeted or sockeye targeted), a variety of play and handling times, angler experience, handling methods, etc. will be represented. To achieve representative samples of C-R sockeye, anglers will be provided with specific gear and told specifically how to approach a particular C-R episode (play time, handling time etc.). It will be critical not to bias the mortality estimate by over- or under-representing any one variable in the C-R sample. For example if careful angler handling is over-represented in the C-R sample than would be observed in the actual fishery this may result in the mortality estimate being biased low.

Given that we are marking individual fish; the individual fish is the experimental unit for survival and standard error calculations. The adjusted mortality rate calculation is described by Nelson (1998) and a model by Wilde et al. (2003). Note: Millard et al. (2005) provide a general template for our study.

This study will be conducted in three time blocks from August to September when most sockeye are caught and released on the Fraser River (a total of three weeks over this period). To ensure net pen effects are balanced over all treatments, the C-R fish and control fish will be placed in relatively equal numbers in each of the three net pens. Roughly equal sample sizes (number of fish caught) should be assigned to the C-R fish and the control; control caught fish should be caught throughout each time block not in a single day or fishing episode. The mortality will be calculated from the proportion of fish that died within the 24-hour period using C-R and control fish in the calculation.

A control group must also be included to estimate mortality (Pollock & Pine 2007). Controls are used to account for effects of fish transport, handling and holding in net pens. Although true controls are not possible for this type of study, fish caught with different methods such as by seine, electro fishing, Mission fish wheel or the use of hatchery held fish are recommended (Millard et al. 2005; Pollock & Pine 2007). We are proposing to catch control fish using beach seine methods. Handling, stress, etc. associated with catching the control sockeye should be minimized by this method (DFO 2000).

OBJECTIVES
  • Determine the logistics and methodology for the 2010 study (Note: should largely be the same as 2009) in a manner where all parties agree (DFO, First Nations, Recreational Fishers)
  • Determine the short-term (24 hour) mortality of sockeye hooked and released from the Fraser River non-tidal fishery for the 2010 season by running the study and compiling results for year 3 (J.O. Thomas)
  • Any changes to methodology as well as a copy of the penultimate report need to be reviewed by the review committee set up through DFO (Debra Sneddon serves as the contact) as well as Peter Nicklin representing FRAFS

METHODS

Study Area
The study will be conducted at Grassy Bar (Appendix 2, Figures 1 and 2); located 4 km downstream of the Island 22 Park boat launch. This is one of the more popular bars on the Fraser River for angling sockeye (Mahoney; 2006). River morphology and current at Grassy Bar also allows segregation of bottom bouncing and bar fishing from this site. The bar must be accessed by boat and its geography allows it to be fished from shore as well as by boat. This study will focus on sampling the catch of shore-based anglers, as intercepting sockeye landed to vessels is not practical (or safe) given the landing challenges of river current and crowding. A total of four staff will work on all facets of the field project. The study area will be marked by signs denoting the upstream and downstream boundaries covered by study technicians, and the demarcation zones for bar fishing and bottom bouncing.

Determination of Sample Size
An a priori analysis was conducted to determine adequate sample sizes needed to provide 95% confidence limits around mortality rates (assuming a very liberal rate of p= 0.50) with a minimal margins of standard error (d=0.08 to 0.03).
Figure 1 illustrates the results of determination of sample size (n) for each margin of error (d) at a 95% confidence interval using the following formula (Gerstman, 2003):

n = 
where n = sample size
and q = 1 - p (where p = 0.5 for our example)
and d = standard error

The analysis suggests that a minimum sample size of 150 fish (per gear type or control group) would be sufficient to achieve a margin of error of 0.08 around the mortality estimate, 95% of the time. More precise margins of error in the range of 0.05 would require samples sizes of approximately 384 sockeye (per gear type or control group).

Sockeye Field Data Collection
Sockeye will be collected from anglers fishing within the defined study area.  Volunteer anglers will either fish under the auspices of a scientific license which allows angling for this study only or during a sanctioned public sockeye opening. Anglers will be provided either bottom bouncing or bar fishing gear; with these gears further partitioned into different leader lengths, hook sizes and line strength, instructions in the conduct of handling fish, responsibilities respecting data collection and identification of their specific gear’s operational boundaries on the bar.

Physiological Sampling
While the sockeye salmon recreational fishery is by tradition a ‘catch and keep’ fishery, the catch and release of fish is common for anglers that have either reached their bag limit or choose to release undersized fish, fish that are beginning to display secondary sexual characteristics, or non-target species (Kristianson and Strongitharm 2006).  Capture by recreational fisheries gear can result in a number of consequences on the physical condition of the fish.  For example hooking injuries, bleeding, scale loss, fin fraying, tissue abrasion, mucous loss, and sub dermal injuries can be common during the hooking, fighting, landing, unhooking, and release procedures.  While the fundamental assumption of catch-and-release is that released fish will have minimal sub lethal impairments and will ultimately survive, little is known about the extent of physical injury caused by recreational fisheries gear capture, and less is known about how this activity affects recovery rates and short-term (i.e. ² 24 h) survival.

Recently, novel approaches that were originally developed in the field of forensic science have been utilized in a fisheries science context to assess the physical condition of fish following capture in fisheries gear (Davis and Ottmar 2006).  Previously, the physical condition of fish has been determined by qualitatively or quantitatively assessing the extent of injuries that could be observed visually.  While visual assessments can be effective for obvious physical injury, this technique can be subjective and often overlooks injury that is not easily observed. Accordingly, the integration of visual assessments with forensic approaches offers a powerful means of more accurately determining the extent of physical injury. Presumptive tests for blood, such as catalytic colour tests (e.g., phenolphthalein, Hemastix¨) or fluorescence/chemiluminescence tests (e.g., Fluorescein, Bluestar(c)) can be used for the rapid, nonlethal assessment of bleeding and abrasion in fish (Noga and Udomkusonsri 2002)

Reporting
The methods and results of the program will be reported to all agencies and participating partners. Program data will be analyzed statistically to quantify mortality levels and possible correlations to fishing method, time played, hook location, injury, sockeye stock timing group and environmental conditions.

* acquire field equipment necessary for the study, including net pen frames/netting/ropes/anchors, fishing gear for the voluntary anglers to standardize this aspect of the study, sockeye sampling and tagging equipment, data record forms, river environment sampling instrumentation and supplies enabling on-site security to oversee the pen site during each of three study phases,
* provide boats to the study for equipment transport,  ferry service for volunteer anglers to the study site, live haul of sockeye, sample platform for the sampling of sockeye into the pen at initial capture and at release following the 24 hour challenge, river access to the study site for the daily collection of environmental parameters including flow, depth, dissolved oxygen and temperature,
* provide fuel for the contractor boats and vehicles towing these boats to the Island 22 boat launch and purchase fuel ‘gift’ cards for voluntary anglers supplying their own boat/transportation, pay for cellular and long distance telephone and fax charges.